METHOD AND DEVICE FOR GENERATING TRAFFIC INFORMATION

Abstract

 A traffic situation (b) of a target road is sampled at predetermined intervals along the road. An array of sampled data obtained thus is divided into a plurality of blocks (block 1, block 2 and block 3). Encoding using orthogonal transform is performed block by block on the sampled data included in each of the blocks. Since the encoded data are decoded block by block, a load on a program for encoding or decoding is reduced so that the memory capacity of a work memory to be used for this process can be saved.

Description

Technical Field

[0001] The present invention relates to a method for generating traffic information, apparatus for generating traffic information in the same method, and apparatus for reproducing the traffic information, so as to obtain the traffic information without imposing a heavy load on an encoding process at the time of generating the traffic information or a decoding process at the time of reproducing the traffic information.

Background Art

[0002] Presently VICS (Vehicle Information and Communication System) offering service to provide road traffic information to car navigation systems etc., gathers road traffic information from vehicle sensors, image sensors, etc. installed on roads, edits this road traffic information, and provides traffic congestion information such as congestion information or travel time information indicating a necessary time, through FM multiplex broadcasting or beacons.

[0003] In current VICS information, current traffic information is expressed as follows.
The situation of traffic congestion is classified and expressed in three stages, that is, heavy congestion (ordinary road: ≤1 0km/h expressway: ≤20km /h), congestion (ordinary road: 10-20km/h, expressway: 20-10km/h) and no congestion (ordinary road: ≥20km/h, expressway: ≥40km/h). When information gathering does not succeed due to a failure in vehicle sensors or the like, the situation is expressed as "unknown".

[0004] When a VICS link (road position information identifier used in VICS) as a whole is in one and the same congestion situation, the congestion information indicating the congestion situation is displayed as:

"VICS link number + state (heavy congestion/ congestion/ no congestion/unknown)"
When congestion occurs in only a part of the link, the information is displayed as:

"VICS link number + congestion head distance (distance from link start terminal) + congestion tail distance (distance from link start terminal) + state (congestion)"
In this case, when the congestion begins at the link start terminal, the congestion head distance is expressed as 0xff. When different congestion states exist together in a link, the congestion states are described individually in this manner.

[0005] On the other hand, link travel time information indicating a travel time of each link is expressed as:

"VICS link number + travel time"

[0006] A car navigation system using this traffic information holds a digital map database in which VICS link numbers are defined in a road network. The car navigation system identifies a target road of the traffic information based on a VICS link number included in VICS information.

[0007] However, the link number defined in the road network has to be replaced by a new number in accordance with new construction, alteration or the like of another road, and digital map data produced by individual companies have to be updated accordingly. Thus, the system in which the position of a road is identified by its link number requires a great deal of social cost for maintenance.

[0008] In order to improve such a point, a method in which a position of a road on a digital map is transmitted without using any common link number has been proposed in Japanese Patent Laid-Open No. 2001-41757. In this method, the transmitting side establishes a plurality of nodes p1, p2, pN in a road section to be transmitted on a transmitting side digital map as shown in Fig. 32(a), and generates "road shape data" in which position data of this plurality of nodes p1, p2,.. pN are arrayed as shown in Fig. 32(b). Then, for example, when a position where an accident occurred in this road section is posted, the road shape data and a distance between a reference node (e.g. p1) and the position of the accident are transmitted to the receiving side. The receiving side performs position identification (including the concept of map matching), by which each node position included in the road position data is associated onto a digital map of the receiving side, so as to identify the road section, so that the position of the accident is identified based on the information of the distance from the reference node.

[0009] In addition, Japanese Patent Laid-Open No. 2003-23357 has disclosed a method in which the road shape data are encoded using a variable length code so as to cut down the amount of data.
The VICS traffic information provided currently can be expressed as shown in Fig. 33, which is a graph whose ordinate designates the number of expressible states of traffic information (traffic expression resolution) and whose abscissa designates the position (or section) resolution. That is, congestion information can be expressed about its position finely by units of 10 m, but the number of expressible states of traffic information is only three, that is, heavy congestion, congestion and nocongestion. Thus, the VICS traffic information can be positioned as information whose position resolution is high but whose traffic expression resolution is low. In addition, the link travel time can be expressed finely by units of 10 seconds. However, the position resolution is limited to only "link unit". Thus, a fine speed distribution in the link cannot be expressed. That is, the link travel time information can be positioned as information whose traffic expression resolution is high but whose position resolution is low.

[0010] In such a manner, the information expressions in the current traffic information are poles apart in resolution, so that expression with intermediate resolution in the circle shown in Fig. 33 cannot be attained.
Traffic information in this circle can be gathered. Original information before edition, which information is gathered by existing sensors, is such intermediate level traffic information though there is a difference in level due to sensor density or the like. In addition, in recent years, a road traffic information gathering system (probe information gathering system or floating car data (FCD) gathering system) which gathers running trajectory information and measured information of speed etc, from running vehicles (probe cars) and uses the gathered information to generate traffic information, has made advances in its studies. In the road traffic information gathering system, information on each level within this circle can be gathered by the center in accordance with the purpose of information gathering or the amount of transmitted data.

[0011] The present inventor et al. have proposed a method in which position resolution and expression resolution of traffic information to be transmitted can be set at any place in Fig. 33.
In this method, a traffic situation expressed by a vehicle speed, a travel time, a degree of congestion, etc, is regarded as a function which is variable along a road, and this function is sampled along the road at an interval corresponding to the position resolution. In addition, obtained sampled data are rounded in accordance with the expression resolution. Figs. 34 show an array of discrete values (sampled data) (b) and a target road (a) obtained thus. Length of each rectangle in Fig. 34(b) designates an interval between sampling points where the traffic situation was sampled.

[0012] This data array of the sampled data is encoded by orthogonal transform, and that encoded data and road shape data indicating a target road section are transmitted to the receiving side. The receiving side identifies the road section using the road shape data, and decodes the encoded data so as to reproduce the sampled data expressing the traffic situation in that section.

[0013] By use of this method, for example, traffic information in a road section of several kilometers can be encoded so that information can be provided with a reduced amount of data. In addition, speed information or the like measured over 4,000 m at intervals of one second by a probe car can be transmitted to the center with a reduced amount of data.

[0014] In this case, as the target road section of the traffic information is set to be longer, a large amount of data can be encoded and compressed in a lump. Thus, the compressibility of data is improved.
The present invention is to improve this method for generating traffic information.

[0015] Indeed, when traffic information is generated in this method, the compressibility of data can be enhanced as the distance of a target road section is increased. However, when the distance of the target road section is long, there occur problems as follows.

[0016] 

(1) When traffic information is encoded or decoded, the number of samples (the amount of data) to be handled in a lump is so large that a large load is imposed on a program. It is therefore difficult to mount the program. In addition, it is necessary to increase the memory size of a work memory to be used for processing of encoding or decoding it is therefore difticuit to realize the method in a PDA, a low-price car navigation system or the like. In addition, it is difficult to make a standardized chip carry out the processing of encoding or decoding.

[0017] (2) When the distance of the target road section is long, it is highly likely that the target road section includes a congestion section for which detailed traffic information is required, and a fine section for which detailed traffic information is not required. It is, however, difficult to change the degree of details of information (compressibility) within one target road section. It is therefore difficult to provide information with details depending on necessity.

[0018] (3) When the distance of the target road section is long, for example, it is likely that the distance from a base point transmitted by the transmitting side is displaced largely on the receiving side. Thus, the displacement in the distance direction of the road is not negligible.
The present invention is to solve the foregoing problems. An object of the present invention is to provide a method for generating traffic information, in which the load on an encoding process or a decoding process is light, the compressibility can be changed easily, and the displacement in the distance direction can be corrected, apparatus for generating traffic information using the same method, and apparatus for reproducing the generated traffic information.

Patent Document 1: Japanese Patent Laid-Open No. 2001-41757

Patent Document 2: Japanese Patent Laid-Open No. 2003-23357

Disclosure of the Invention

[0019] A method for generating traffic information according to the present invention is a method for generating traffic information in which a traffic situation of a target road is sampled at predetermined intervals along the road, including the steps of: dividing an array of sampled data into a plurality of blocks; and encoding the sampled data included in the blocks block by block by orthogonal transform.

[0020] The encoded data are also decoded block by block. Accordingly, the load on the program for encoding or decoding can be reduced so that the memory capacity of a work memory to be used for this process can be saved.
In addition, in the method for generating traffic information according to the present invention, the number of pieces of the sampled data included in each of the blocks is set to be not larger than a predetermined upper limit number.

[0021] If there is no limit in the number of pieces of sampled data included in encoded data, the receiving side of the traffic information will have to be ready for processing to be able to support a large number of pieces of sampled data. However, when there is an upper limit in the number of pieces of sampled data, the receiving side can be prepared for it easily.

[0022] In addition, in the method for generating traffic information according to the present invention, the number of pieces of the sampled data included in each of the blocks is set to be fixed,
In such a manner, a decoding mechanism of receiving side equipment of the traffic information can be standardized.

[0023] In addition, in the method for generating traffic information according to the present invention, the target road is divided into sections at constant distance intervals, and the blocks are generated correspondingly to the divided sections.
In such a manner, the process for encoding/decoding the traffic information can be standardized.

[0024] In addition, in the method for generating traffic information according to the present invention, the target road is divided into sections at non-equidistant intervals with selected places set as boundaries, and the blocks are generated correspondingly to the divided sections.
In addition, places of crossings or facilities are selected as the boundaries

[0025] In this system, a section where a change in a traffic flow occurs constantly can be included in one block. Thus, the traffic information can be displayed more easily to understand.
In addition, in the method for generating traffic information according to the present invention, the sampled data are divided by time so as to generate the blocks.

[0026] In addition, when the sampled data are measured information measured by probe car on-vehicle equipment, the measured information is divided into a plurality of pieces by time zone of measuring time, and the blocks are generated in accordance with the divided pieces of the measured information.

[0027] In such a manner, the blocks may be divided by time.
In addition, in the method for generating traffic information according to the present invention, when the sampled data are measured information measured by probe car on-vehicle equipment, block markers indicating boundaries between the blocks are set based on at least one of running information in the probe car on-vehicle equipment, position information on map information where a position of the probe car on-vehicle equipment is associated, and communication operation information in a communication portion mounted on the probe car on-vehicle equipment.

[0028] In such a manner, for example, the blocks can be divided with block markers set in turning points of the traffic situation in accordance with the running condition of the probe car on-vehicle equipment. Thus, the turning points of the traffic information can be distinguished easily.

[0029] In addition, in the method for generating traffic information according to the present invention, the aforementioned block markers are set when predetermined events occur during travel of the aforementioned probe car on-vehicle equipment based on at least one of the aforementioned running information, the aforementioned position information and the aforementioned communication operation information.

[0030] In such a manner, for example, when a block marker is set in the case where there occurred a predetermined event such as turning right/left at a crossing or entering facilities, a turning point of traffic information can be distinguished easily so that blocks can be set and divided in accordance with the section where the traffic situation is changed. In addition, the turning point of the traffic information can be distinguished easily even when measured information is averaged by encoding block by block.

[0031]  In addition, in the method for generating traffic information according to the present invention, data compressibility in encoding is set by unit of the blocks.
Thus, the traffic information can be encoded in necessary details in accordance with the traffic situation.

[0032] The data compressibility is changed in accordance with an average speed in the blocks expressed by the sampled data.
Alternatively, the data compressibility is changed in accordance with a rate of change in average speed of the blocks expressed by the sampled data between adjacent ones of the blocks.

[0033] Alternatively, the data compressibility is changed in accordance with an event occurring in a section corresponding to each of the blocks.
Alternatively, the data compressibility in each block including measured information of the probe car on-vehicle equipment as the sampled data is changed in accordance with an event measured by the probe car on-vehicle equipment, such as braking suddenly.

[0034] Alternatively, the data compressibility is changed in accordance with measuring time of the measured information measured by the probe car on-vehicle equipment.
Alternatively, the data compressibility is changed in accordance with whether a measuring place of the measured information measured by the probe car on-vehicle equipment is near a specified position or not.

[0035] In addition, in the method for generating traffic information according to the present invention, in encoding by unit of the blocks, a range of each of the blocks is extended, and encoding is performed on sampled data of the block including sampled data of an extension portion thereof.

[0036] In such a manner, mismatching (block noise) which may occur in a boundary between blocks at the time of decoding can be reduced.
In order to reduce the block noise, values of sampled data in the extension portion are brought into agreement with values of sampled data in an original boundary of the block.

[0037] Alternatively, values of sampled data in the extension portion are brought into agreement with values of corresponding sampled data of a block adjacent to the block.
Alternatively, values of sampled data in the extension portion are brought into agreement with values of corresponding sampled data of a block adjacent to the block, the sampled data of the block including the extension portion are multiplied by a window function, and values obtained thus are set as sampled data of the block.

[0038] In addition, in the method for generating traffic information according to the present invention, position information indicating boundaries between the blocks is added to road reference data for specifying the target road, so as to form a part of the traffic information.
The receiving side of the traffic information can correct a displacement in the distance direction of the target road using the position information indicating boundaries between the blocks so that the traffic information can be reproduced accurately on the digital map of the receiving side.

[0039] A method for reproducing traffic information according to the present invention is a method for reproducing traffic information, in which a traffic situation of a target road is sampled at predetermined intervals along the road, including the steps of: acquiring traffic information generated by dividing an array of sampled data into a plurality of blocks and encoding the sampled data by unit of the aforementioned blocks; and decoding the aforementioned traffic information block by block so as to reproduce the sampled data.

[0040] In such a manner, the traffic information is decoded block by block so that the load on a program can be reduced, and the memory capacity of a work memory used for this process can be saved.
In addition, in the method for reproducing traffic information according to the present invention, in reproducing the sampled data, the traffic information is output to be associated with position information.

[0041] Alternatively, in reproducing the sampled data, the traffic information is displayed on a display portion so as to be associated with position information.
In such a manner, the traffic information is decoded block by block so that the load of processing can be reduced when the traffic information reproduced for output, display or the like is made good use of.

[0042] In addition, the present invention provides a program for making a computer execute respective procedures of a method for generating traffic information according to any one of the aforementioned configurations.
In addition, the present invention provides a program for making a computer execute respective procedures of a method for reproducing traffic information according to any one of the aforementioned configurations.

[0043] Apparatus for generating traffic information according to the present invention is apparatus for generating traffic information, in which a traffic situation of a target road is sampled at predetermined intervals along the road, including: a block.dividing portion for dividing an array of sampled data corresponding to the aforementioned traffic situation into a plurality of blocks; and an encoding portion for encoding the aforementioned sampled data included in the aforementioned blocks block by block by orthogonal transform.

[0044] In such a manner, the traffic information is encoded block by block so that the load on a program can be reduced, and the memory capacity of a work memory used for this process can be saved.
In addition, the apparatus for generating traffic information according to the present invention, includes: a traffic information blocking portion for dividing an array of sampled data into a plurality of blocks, a traffic situation of a target road having been sampled in the sampled data; a block-by-block compressibility deciding portion for deciding compressibility in encoding the sampled data included in each of the blocks; a block noise reduction process portion for performing a process for reducing block noise generated in boundaries between the blocks in decoding; and an orthogonal transform encoding process portion for encoding the sampled data in the blocks subjected to the block noise reduction process, block by block by orthogonal transform.

[0045] In this apparatus, the traffic information can be encoded by use of the small blocks, and the compressibility in encoding can be set by unit of the small blocks.
In addition, the apparatus for generating traffic information according to the present invention, further includes a block position marker adding portion for adding position information of block markers to road reference data specifying the target road, the biock markers indicating boundaries between the blocks; wherein encoded data generated by the orthogonal transform encoding process portion and the road reference data added with the position information of the block markers are provided.

[0046] The receiving side can identify the target road and a break in the blocks from the road reference data.
In addition, in the apparatus for generating traffic information according to the present invention, the block position marker adding portion divides the aforementioned target road into sections at predetermined distance intervals, and sets the block markers correspondingly to the divided sections.

[0047] In such a manner, for example, the blocks are divided into predetermined distance sections such as predetermined distance intervals, so that the traffic information can be encoded block by block.
In addition, in the apparatus for generating traffic information according to the present invention, when the aforementioned sampled data are measured information measured by probe car on-vehicle equipment, the block position marker adding portion divides the aforementioned measured information into pieces at predetermined time intervals, and sets the block markers correspondingly to the divided pieces of the measured information.

[0048] In such a manner, blocks are divided at predetermined time intervals such as constant time intervals, so that the traffic information can be encoded block by block.
In addition, in the apparatus for generating traffic information according to the present invention, when the aforementioned sampled data are measured information measured by probe car on-vehicle equipment, the block position marker adding portion sets the block markers based on at least one of running information in the aforementioned probe car on-vehicle equipment, position information on map information with which a position of the aforementioned probe car on-vehicle equipment is associated, and communication operation information in a communication portion mounted on the aforementioned probe car on-vehicle equipment.

[0049] In such a manner, for example, the blocks can be divided with block markers set in turning points of the traffic situation in accordance with the running condition of the probe car on-vehicle equipment. Even when the measured information is averaged due to encoding block by block, the turning points of the traffic information can be distinguished easily.

[0050] Apparatus for reproducing traffic information according to the present invention is apparatus for reproducing traffic information, in which a traffic situation of a target road is sampled at predetermined intervals along the road, including: an acquiring portion for acquiring traffic information generated by dividing an array of sampled data corresponding to the aforementioned traffic situation into a plurality of blocks, and encoding the sampled data by unit of the aforementioned blocks; and a reproducing portion for decoding the aforementioned traffic information block by block so as to reproduce the sampled data.

[0051] In such a manner, the traffic information is decoded block by block so that the load on a program can be reduced, and the memory capacity of a work memory used for this process can be saved.
In addition, according to the present invention, apparatus for reproducing traffic information, includes: a receiving portion for receiving traffic information and road reference data, the traffic information being obtained by dividing sampled data indicating a traffic situation of a target road into blocks and encoding the sampled data by unit of the blocks, the road reference data indicating the target road and boundary positions between the blocks; a traffic information decoding portion for decoding the traffic information block by block so as to reproduce the sampled data; a block noise reduction processing portion for excluding sampled data added thereto in order to reduce block noise, from the reproduced sampled data, and acquiring sampled data included in a range of each of the blocks; a block-by-block correction coefficient calculating portion for calculating correction coefficients for correcting a displacement occurring in a distance direction of the target road by use of information of boundary positions between the blocks included in the road reference data; and a block-by-block unit distance correcting portion for identifying a correct position of each of the blocks on the target road by use of the correction coefficients, and positioning the sampled data in sampling positions of the block.

[0052] This apparatus for reproducing traffic information decodes the traffic information by use of small blocks, so that the load on a program can be reduced, and the memory capacity of a work memory can be saved. In addition, the position of each block can be identified properly on the digital map of the apparatus itself by use of information of the boundary positions of the block, and the sampled data can be positioned properly in the sampling positions within the block.

[0053] In the method for generating traffic information according to the present invention, traffic information of a target road is divided into small blocks and encoded, so that the load on a program can be reduced, and it is sufficient to use a small-size memory as a work memory to be used for the process of encoding or decoding. Accordingly, the encoding/decoding process can be left to a semiconductor chip.

[0054] In addition, the compressibility of the traffic information can be changed by unit of the small blocks. Accordingly, the fineness of the traffic information can be set in accordance with necessity.
In addition, the displacement in the distance direction of a road can be corrected by use of the boundary positions of each block of the traffic information. Accordingly, high-precision traffic information can be transmitted.

Brief Description of the Drawings

[0055] 

Figs. 1 is schematic diagrams for explaining a method for generating traffic information according to a first embodiment of the present invention.

Fig. 2 is a block diagram showing the configuration of information transmitting apparatus and the configuration of information use apparatus according to the first embodiment of the present invention.

Fig. 3 is diagrams showing running trajectory/measured data of a probe car and block marker information according to the embodiment of the present invention.

Fig. 4 is a flow chart showing a procedure to add block markers to probe car measured information according to the first embodiment of the present invention.

Fig. 5 is diagrams showing road shape data/traffic information and block marker information according the embodiment of the present invention.

Fig. 6 is a flow chart showing a procedure to add block markers to road shape data/traffic information according to the first embodiment of the present invention.

Fig. 7(a) shows a DWT filter circuit, and Fig. 7(b) shows an IDWT filter circuit.

Fig. 8(a) shows a lifting configuration of the DWT filter circuit, and Fig. 8(b) shows a lifting configuration of the IDWT filter circuit.

Fig. 9 is a flow chart showing a procedure of an orthogonal transform encoding process according the embodiment of the present invention.

Fig. 10 is views showing a change in data due to DWT.

Fig. 11 is a view for explaining a part of transmission data.

Fig. 12 is diagrams showing parameter information and traffic information generated in the method according to the embodiment of the present invention.

Fig. 13 is a diagram showing a boundary value extending system used in a block noise reduction method according to the embodiment of the present invention.

Fig. 14 is a flow chart showing a procedure of the boundary value extending system according to the embodiment of the present invention.

Fig. 15 is a diagram showing parameter information generated in the boundary value extending system according to the embodiment of the present invention.

Fig. 16 is a diagram showing an out-of-boundary encoding system used in a block noise reduction method according to the embodiment of the present invention.

Fig. 17 is a flow chart showing a procedure of the out-of-boundary encoding system according to the embodiment of the present invention.

Fig. 18 is diagrams for explaining a window function usage system used in a block noise reduction method according to the embodiment of the present invention.

Fig. 19 is a flow chart showing a procedure of the window function usage system according to the embodiment of the present invention.

Fig. 20 is a diagram showing parameter information generated in the window function usage system according to the embodiment of the present invention.

Fig. 21 is diagrams showing the data configurations of road shape data, block marker information and traffic information generated in the method for generating traffic information according to the embodiment of the present invention.

Fig. 22 is a diagram for explaining another block marker setting method in the method for generating traffic information according to the embodiment of the present invention.

Fig. 23 is a diagram showing the relationship between the resampling length and the number of bits required for displaying a node-to-block-marker distance.

Fig. 24 is a diagram showing another data structure of road shape data generated in the method for generating traffic information according to the embodiment of the present invention.

Fig. 25 is a now chart showing a procedure of an IUW-I- process.

Fig. 26 is Diagrams for explaining a displacement correction method according to the embodiment of the present invention.

Fig. 27 is a schematic diagram showing a modification of the method for generating traffic information according to the embodiment of the present invention.

Fig. 28 is a schematic diagram showing a first example and a second example of a method for generating traffic information according to a second embodiment of the present invention.

Fig. 29 is a schematic diagram showing a third example and a fourth example of the method for generating traffic information according to the second embodiment of the present invention.

Fig. 30 is a block diagram showing the configuration of information transmitting apparatus and the configuration of information use apparatus according to the second embodiment of the present invention.

Fig. 31 is a flow chart showing a procedure to add block markers to probe car measured information according to the second embodiment of the present invention.

Figs. 32is diagrams for explaining road shape data.

Fig. 33 is a diagram for explaining position resolution and expression resolution of traffic information.

Figs. 34 is diagrams for explaining a method for expressing traffic information regarded as a function of a road.

Best Mode for Carrying Out the Invention

(First Embodiment)

[0056] In a method for generating traffic information according to an embodiment of the present invention, traffic information positioned at an equal interval along a target road is divided into blocks at a constant distance (that is, a constant number of sampling points), and the traffic information is encoded for each of these small blocks, as shown in Fig. 34(b). Then, road shape data of the target road expressly providing a divided section of the traffic information, and the traffic information encoded for each small block are transmitted to the receiving side. The receiving side decodes the small blocks of the traffic information individually, and connects the obtained pieces of the traffic information so as to reproduce the traffic information of the target road.

[0057] in this case, the number of samples (the amount of data) included in each small biock corresponds to the number of samples (the amount of data) to be handled in a lump when the traffic information is encoded and decoded. Thus, the load on a program becomes lighter, and it is enough to use a small-memory-size work memory for encoding and decoding the traffic information.

[0058] Figs. 1 schematically show this method for generating traffic information.
Fig. 1(a) shows a target road of traffic information. Fig. 1(b) is a graph showing a running speed measured at intervals of unit time by a probe car. In Fig. 1 (b), the ordinate designates the speed, and the abscissa designates the distance from a base point of the target road. This graph is nothing but a graph of traffic information expressed in the form of Fig. 34(b) in spite of a difference in interval of sampling points. This speed information may be regarded as traffic information transmitted from a probe car to the center or as traffic information gathered from the probe car and provided to a car navigation system or the like by the center.

[0059] Incidentally, in the graph of Fig. 1 (b), the solid line designates measured data of speed, the one-dot chain line designates speed information in which measured data have been compressed at a low compressibility, the fine broken line designates speed information in which the measured data have been compressed at a middle compressibility, and the rough broken line designates speed information in which the measured data have been compressed at a high compressibility.

[0060] The traffic information is divided by unit of 1,000 m here. Block markers indicating the positions of boundaries of blocks of traffic information are set on the target road, and road shape data of the target road are generated to distinguish positions of the block markers (setting of block markers). In Fig. 1(a), nodes for obtaining the road shape data are set at intervals of distance L1 in a tight-curve section having a large curvature of the target road, and at intervals of distance L2 (>L1) in a gentle-curve section having a small curvature, and the block marker positions are added to the nodes. Incidentally, identification information of nodes adjacent to the block markers and information of distances to the nodes may be held in spite of the block marker positions added as nodes.

[0061] The traffic information divided into blocks is encoded block by block by orthogonal transform ("orthogonal transform encoding process"), In this event, the compressibility of encoded data is set block by block (block-by-block setting of compressibility).

[0062] In addition, when the traffic information encoded block by block is decoded and pieces of information of the blocks obtained thus are connected, it is likely that mismatching (block noise) occurs in boundaries of blocks. To avoid this, a process to reduce the block noise is performed in advance ("block noise reduction process").

[0063] The traffic information encoded block by block is provided together with the road shape data of the target road.
The receiving side receiving these pieces of information identifies the target road from the road shape data, and positions the traffic information decoded block by block, onto the target road. In this event, the displacement in the length direction of the target road is corrected by use of the distance information between the block markers ("distance displacement correction process").

[0064] Fig. 2 is a block diagram showing the configuration of information transmitting apparatus 10 for providing traffic information generated in this method, and the configuration of information use apparatus 40 for making good use of the provided traffic information. The information transmitting apparatus 10 is probe car on-vehicle equipment for transmitting probe information, or a traffic information center for providing edited traffic information. On the other hand, the information use apparatus 40 is a probe information gathering center for gathering the probe information, or a car navigation system or the like to be provided with the traffic information.

[0065] The information transmitting apparatus 10 has traffic information/measured information input portions 11 which are positioned at an equal interval along a road and to which measured information or traffic information is input, a traffic information blocking portion 14 which generates traffic information block by block from the input information, a block-by-block compressibility deciding portion 16 which sets compressibility of the traffic information block by block, a block noise reduction process portion 17 which performs a block noise reduction process, an orthogonal transform encoding process portion 19 which performs an orthogonal transform encoding process on the biock-by-biock traffic information, a digital map database (A) 12, a shape data extracting portion 13 which generates a running trajectory of a probe car or road shape data of a target road of the traffic information from the input information, a block position marker adding portion 15 which adds block markers to the road shape data, a variable length encoding process portion 18 which encodes the road shape data using a variable length code, a data transmitting portion 20 which transmits the traffic information encoded block by block and the road shape data, and a data accumulating portion 21 which accumulates the traffic information and the road shape data and provides them through external media.

[0066] On the other hand, the information use apparatus 40 has a data receiving portion 41 which receives data transmitted from the information transmitting apparatus 10, an encoded shape data decoding portion 42 which decodes road shape data encoded by a variable length code, a shape data restoring portion 43 which restores the road shape data, a digital map database (B) 45, a position identifying portion 44 which identifies a road expressed by the road shape data on a digital map of the digital map database (B) 45, a blocking position identifying portion 46 which identifies positions of block markers, a block-by-block correction coefficient calculating portion 47 which calculates correction coefficients to be used for a distance displacement correction process, an encoded traffic information data decoding portion 48 which decodes block-by-block traffic information encoded by orthogonal transform, a block noise reduction process portion 49 which performs a block noise reduction process upon the decoded traffic information, a block-by-block unit distance correcting portion 50 which corrects positions of sampling points in each block or the like, a traffic information superimposing portion 51 which superimposes the traffic information on a target road, and an information use portion 52 which makes good use of the traffic information.

[0067] The information transmitting apparatus 10 constitutes an encoder from the point of view of generation of encoded data, while the information use apparatus 40 constitutes a decoder from the point of view of restoration of the encoded data.
Description will be made in detail about a traffic information generating method to be performed in this information transmitting apparatus 10.

<Setting of Block Markers>

[0068] When the information transmitting apparatus 10 is probe car on-vehicle equipment, measured information such as coordinates of sampling points (nodes), and measured times, distances between the sampling points, speeds, etc. measured at the sampling points, are input from the traffic information/measured information input portion 11 as shown in Fig. 3(a). The traffic information blocking portion 14 generates block-by-block traffic information from this input information. The shape data extracting portion 13 selects coordinates of sampling points from this input information and generates road shape data of a running trajectory. The block position marker adding portion 15 adds information of block markers to the road shape data.

[0069] This block marker setting process is performed in the procedure shown in Fig. 4.
A fixed distance (or a fixed number of sampling points) is set in advance as unit with which each block marker will be added. Alternatively, this distance may be settled dynamically in accordance with a free memory capacity available as a work memory for encoding.

[0070] Measurement is repeated every unit time (or at a fixed distance interval) till it is time to transmit probe information to the probe information gathering center, and measured data are accumulated in a buffer (Step 1). When it is time to transmit the probe information (Step 2), the traffic information blocking portion 14 decides the unit with which each block marker will be added (Step 3), and using that unit to set block markers in the measured information input from the traffic information/measured information input portion 11, so as to generate block marker information shown in Fig. 3(b).

[0071] When a fixed distance (or a fixed number of sampling points) is settled in advance as the unit with which each block marker will be added, the number of a node where the accumulated value of inter-node distance data (or the number of sampling points) of the input measured information reaches the distance (or the number of sampling points) serving as the unit with which each block marker will be added is written into the block marker information whenever such a node emerges. On the other hand, when the distance serving as the unit with which each block marker will be added is settled dynamically in accordance with a free memory capacity, a current free memory capacity is measured, and the distance (or the number of sampling points) serving as the unit with which each block marker will be added is decided from the value of the current free memory capacity.

[0072] The traffic information blocking portion 14 also extracts measured data such as a measuring time, a distance between sampling points, a speed, etc. from the measured information where the block markers have been set, and generates block-by-block measured information (Step 5). The traffic information blocking portion 14 sends the generated block marker information to the block position marker adding portion 15, and the block position marker adding portion 15 adds position information of the block markers to the road shape data of the running trajectory generated by the shape data extracting portion 13, based on the block marker information (Step 6).

[0073] On the other hand, when the information transmitting apparatus 10 is a center for providing traffic information, coordinates of sampling points (nodes), distances between the sampling points, and traffic information positioned in the sampling points are input from the traffic information/measured information input portion 11 as traffic information of a large number of roads as shown in Fig. 5(a).

[0074] The traffic information blocking portion 14 generates block-by-block traffic information from this input information. The shape data extracting portion 13 selects coordinates of sampling points from this input information and generates road shape data of a target road of the traffic information. The block position marker adding portion 15 adds information of block markers to the road shape data.

[0075] This block marker setting process is performed in the procedure shown in Fig. 6. A fixed distance (or a fixed number of sampling points) is set in advance as unit with which each block marker will be added. Alternatively, this distance may be settled dynamically in accordance with a request from mate apparatus in an interactive system.

[0076]  When shape data and traffic information (Fig. 5(a)) are input through the traffic information/measured information input portion 11 sequentially in order of increasing identification number from the identification number 1 (Step 10 and Step 11), the traffic information blocking portion 14 decides the unit with which each block marker will be added (Step 12), and sets the block markers on the input information by the decided unit so as to generate block marker information shown in Fig. 5(b) (Step 13).

[0077] When a fixed distance (or a fixed number of sampling points) is settled in advance as the unit with which each block marker will be added, the number of a node where the accumulated value of inter-node distance data (or the number of sampling points) of the input measured information reaches the distance (or the number of sampling points) serving as the unit with which each block marker will be added is written into the block marker information whenever such a node emerges. On the other hand, in the case of an interactive system, a block marker is set for every distance (or number of sampling points) demanded by the mate apparatus.

[0078] The traffic information blocking portion 14 also extracts pieces of traffic information positioned in sampling points block by block from the input information where the block marker have been set, and generates block-by-block traffic information (Step 14). The traffic information blocking portion 14 sends the generated block marker information to the block position marker adding portion 15, and the block position marker adding portion 15 adds position information of the block markers to the road shape data of the target road of the traffic information generated by the shape data extracting portion 13, based on the block marker information (Step 15).

[0079] Such a process is repeated all over the shape data till the setting of the block markers is terminated (Step 16 and Step 17). The traffic information blocking portion 14 constitutes a block dividing portion (traffic information blocking portion) for dividing a sampled data array corresponding to a traffic situation into a plurality of blocks.

<Setting of Compressibility Block by Block>

[0080] The block-by-block compressibility deciding portion 16 sets the compressibility of each block of the traffic information generated by the traffic information blocking portion 14, as follows.

[0081] (1) In the case where the information transmitting apparatus 10 is a traffic information providing center or probe car on-vehicle equipment, detailed information is required when there is a large difference in speed between blocks. Thus, the compressibility is set to be low. Specifically, an average speed in each block is calculated, and the compressibility is changed in accordance with the difference from an average speed in a block adjacent thereto.

[0082] (2) In the case where the information transmitting apparatus 10 is a traffic information providing center, detailed information is required when there occurs an event of an incident such as an accident, construction, regulation, etc. Thus, the compressibility is set to be low. Specifically, it is determined whether there is or not an event of an incident such as an accident, construction, regulation, etc. in each block, and the compressibility is changed in accordance with the degree of influence (the number of regulated lanes or the like) of the event on a traffic flow.

[0083] (3) In the case where the information transmitting apparatus 10 is probe car on-vehicle equipment, the compressibility is changed in accordance with the existence of an event of measurement. For example, the compressibility is reduced when brakes are hit suddenly. Specifically, it is determined whether an event specified in advance occurs in each block or not, and the compressibility is changed in accordance with the contents of the event.

[0084] (4) In the case where the information transmitting apparatus 10 is probe car on-vehicle equipment, the information freshness of measured information is degraded with the passage of time since measurement. Thus, the compressibility is set to be high. Specifically, the time at the last (or first) measurement point in each block is calculated, and the compressibility is changed in accordance with the passage of time.

[0085] (5) In the case where the information transmitting apparatus 10 is probe car on-vehicle equipment, the compressibility near a position specified from the information gathering center is changed. Specifically, it is determined whether a place specified from the information gathering center is present in each block or not, and the compressibility in the block where the specified place is present is changed to specified compressibility.

<Orthogonal Transform Encoding Process>

[0086] Next, description will be made about the orthogonal transform encoding process to be performed by the orthogonal transform encoding process portion 19 before the block noise reduction process.

[0087] Here, description will be made about the case where discrete wavelet transform (DWT) is used as the orthogonal transform.
This DWT can be realized by a filter circuit dividing a low frequency band recursively. On the other hand, inverse DWT (IDWT) can be realized by a filter circuit repeating synthesis inverse to the division. Although various filter configurations can be formed as DWT, the following description will be made about an example using a 2x2 DWT filter (filter generating one wavelet coefficient and one scaling coefficient from two inputs).

[0088] Fig. 7(a) shows a DWT filter circuit. This DWT circuit is constituted by cascade connection of a plurality of circuits 191, 192 and 193 each having a low pass filter 181, a high pass filter 182 and a thinning circuit 183 for thinning signals to 1/2. After passing through the high pass filter 182, a high frequency component of a signal input to the circuit 191 is thinned to 1/2 by the thinning circuit 183 and output. After passing through the low pass filter 181, a low frequency component of the signal is thinned to 1/2 by the thinning circuit 183 and input to the next circuit 192. Fig. 8(a) shows a specific configuration of each circuit 191, 192, 193. "Round" in Fig. 8(a) designates a rounding process.

[0089] When two pieces of data are input to this circuit 191, the data are transformed into one high frequency component data (this will be referred to as a wavelet coefficient) and one low frequency component data (this will be referred to as a scaling coefficient). This scaling coefficient indicates information of smoothed (averaged) input data. On the other hand, the wavelet coefficient indicates differential information for restoring original data from the scaling coefficient.

[0090] When 2² pieces of data are input to the circuit 191, two wavelet coefficients and two scaling coefficients are generated. When the two scaling coefficients are input to the circuit 192, one wavelet coefficient and one scaling coefficient are generated in the same manner. A wavelet coefficient and a scaling coefficient generated in the circuit 191 are referred to as a primary wavelet coefficient and a primary scaling coefficient respectively. A wavelet coefficient and a scaling coefficient generated in the circuit 192 are referred to as a secondary wavelet coefficient and a secondary scaling coefficient respectively.

[0091] Similarly, when 2³ pieces of data are input to the circuit 191, four primary wavelet coefficients and four primary scaling coefficients are generated. When the four primary scaling coefficients are input to the circuit 192, two secondary wavelet coefficients and two scaling coefficients are generated. When the two secondary scaling coefficients are input to the circuit 193, one tertiary wavelet coefficient and one tertiary scaling coefficient are generated.

[0092] Thus, the number of pieces of input data has to be a multiple of the N-th power of 2 in the 2×2 filter.
Fig. 7(b) shows an IDWT filter circuit. The IDWT circuit is constituted by cascade connection of a plurality of circuits 194, 195 and 196 each having an interpolation circuit 186 for doubling a signal by interpolation, a lower pass filter 184, a high pass filter 185, and an adder 187 for adding the outputs of the low pass filter 184 and the high pass filter 185. Low frequency component and high frequency component signals input to the circuit 194 are doubled by interpolation, added to each other, and input to the next circuit 195. Fig. 8(b) shows a specific configuration of each circuit 194, 195, 196.

[0093] Now, when one tertiary scaling coefficient and one tertiary wavelet coefficient generated by the filter circuit in Fig. 7(a) are input to the circuit 194 as a low frequency component and a high frequency component respectively, two secondary scaling coefficients are reproduced by the circuit 194. When one of these secondary scaling coefficients and one secondary wavelet coefficient are input to the circuit 195 as a low frequency component and a high frequency component respectively, two primary scaling coefficients are reproduced. Accordingly, four primary scaling coefficients can be reproduced by the combination of two secondary scaling coefficients and two wavelet coefficients. In the same manner, 2³ input data can be reproduced by the circuit 196 by the combination of the four primary scaling coefficients reproduced by the circuit 195 and four primary wavelet coefficients.

[0094] That is, by use of one tertiary scaling coefficient, one tertiary wavelet coefficient, two secondary wavelet coefficients and four primary wavelet coefficients transformed from eight pieces of input data by the filter circuit in Fig. 7(a), the eight pieces of input data can be reproduced.

[0095] Here, it should be noted that four primary scaling coefficients can be reproduced in spite of absence of four primary wavelet coefficients, and the conditions of the eight pieces of input data can be known with rough resolution by these scaling coefficients. In addition, two secondary scaling coefficients can be reproduced only from one tertiary scaling coefficient and one tertiary wavelet coefficient, and the conditions of the input data can be known with rougher resolution by these scaling coefficients.

[0096] In Fig. 1(b), the graph shown as high compression indicates the transition of speed using lower-order scaling coefficients obtained by DWT transform of speed data. In addition, the graph shown as middle compression indicates the transition of speed using middle-order scaling coefficients, and the graph shown as low compression indicates the transition of speed using high-order scaling coefficients

[0097] The flow chart of Fig. 9 shows a procedure of DWT on block-by-block traffic information, preprocessing and post-processing of the DWT. The processing from Step 20 to Step 28 show the preprocessing as far as a multiple of the N-th power of 2 of pieces of input data are arranged from block-by-block traffic information. In the processing, the block-by-block traffic information is sampled at intervals corresponding to the position resolution (distance resolution) and subjected to a rounding process in accordance with the expression resolution so as to generate an integral multiple of 2^N of pieces of input data. When the number of pieces of input data does not coincide with any integral multiple of 2^N, 0 or the last numerical value is added as a dummy so that the both coincide with each other.

[0098] Next, in order to reduce the absolute value of the input data, the level of each piece of data is shifted by the intermediate value of the input data (Step 29), and the order number N of DWT is decided (Step 30). This corresponds to determining how many filter circuits connected in cascade in Fig. 7(a) should be used to perform DWT.

[0099] Next, sequentially in order of increasing order from zero (n=0) (Step 30), the number of pieces of input data is decided by (number of pieces of data)/2ⁿ (Step 32), and DWT is applied to the input data so as to decompose the input data into scaling coefficients and wavelet coefficients (Step 33). In this event, the number of scaling coefficients and the number of wavelet coefficients are 1/2 of the number of pieces of input data respectively.

[0100] The obtained scaling coefficients and the obtained wavelet coefficients are stored in front of and at the rear of the data respectively (Step 34). When n<N (Step 35), the routine of processing returns to Step 32, where the order is increased by one, and the number of pieces of input data is decided by (number of pieces of data)/2ⁿ. In this event, only the scaling coefficients stored in front in Step 34 are used as the next input data.

[0101] The processing from Step 32 to Step 34 is repeated until n=N. As a result of this processing, the number of scaling coefficient is one when the number of pieces of input data is 2^N. The number of scaling coefficient is m when the number of pieces of input data is m×2^N.

[0102] Next, the data generated by DWT are decomposed by a bit plane (Step 36), and arithmetic coding is performed on bit data binarized thus (Step 37).
Figs. 10 show input data (a) of one block of traffic information in which a dummy is added to Nb pieces of available data so that the number of pieces of data is adjusted to Na (=2^N), scaling coefficients and wavelet coefficients (b) generated by performing N-order DWT on the input data, and a result (c) of bit plane decomposition of the scaling coefficients and the wavelet coefficients. An upper piece (that is, higher order piece) of the bit-plane decomposed data has higher importance, and a left side piece (that is, upper digit piece) of the data has higher importance. Accordingly, as shown in Fig. 11, when n or higher order bit-plane data excluding lower L digits are sent to the receiving side, the essence of the traffic information can be transmitted, and the traffic information can be reproduced with resolution rough but fine enough to know the traffic situation on the receiving side.

[0103] Figs. 12 show transmitting data (b) in which one block of traffic information is expressed by coefficients of DWT, and parameter information (a) thereof. The parameter information (a) includes various pieces of information such as the length of the block, the number Na of pieces of data (the number of divisions of the block), the number Nb of pieces of available data, the DWT final order N, the DWT transmitting order n indicating the DWT minimum order included in the transmitting data, and the level shaft L indicating the number of digits excluded from the transmitting data. The transmitting data (b) include N-order scaling coefficients and N-order to n-order wavelet coefficients whose lower L digits are excluded. When the values Na, N and L are changed block by block, the compressibility can be changed block by block. The compressibility set in the "setting of compressibility block by block" can be attained by changing these parameters. Incidentally, when the value Na is made uniform all over the blocks, program processing can be carried out easily.

[0104] The orthogonal transform encoding process portion 19 constitutes an encoding portion for encoding sampled data included in each block by orthogonal transform block by block.

<Block Noise Reduction Process>

[0105] The block noise reduction process portion 17 reduces block noise in the following methods (1), (2) and (3).

[0106] (1) The value of each block boundary portion is extended directly, and compression encoding is performed including a portion outside the boundary to some extent (referred to as "boundary value extending system"). At the time of restoration, the information outside the block boundary is abandoned.

[0107] 

(2) Compression encoding is performed including data out of an original boundary of each block to some extent (referred to as "out-of-boundary encoding system"). At the time of restoration, the information outside the block boundary is abandoned.

(3) A window function with attenuation at opposite ends is defined, and encoding is performed so that adjacent blocks overlap with each other (referred to as "window function usage system").

[0108]  In these systems, it is necessary to encode a range wider than an original range. Therefore, these systems lead to increase in amount of data. However, each system is a process necessary to reduce block noise.
Next, each System will be described in detail.

[0109] (1) Boundary Value Extending System
In the boundary value extending system, as shown in Fig. 13, a range (range surrounded by the broken line, which will be referred to as "to-be-encoded traffic information range") of traffic information where input data will be sampled for generating to-be-transmitted data (encoded data) of an intended block K is extended to the outside of the range of the intended block K. The value of the traffic information in the extension range on the upstream side is set to be equal to the value in the upstream boundary of the intended block K. The value of the traffic information in the extension range on the downstream side is set to be equal to the value in the downstream boundary of the intended block K.

[0110] The flow chart of Fig. 14 shows the procedure of encoding in this system. First, the number M of blocks of traffic information to be provided is acquired (Step 40). Sequentially in order of increasing block number from the block number K=1 (Step 41), traffic information of the block K is acquired (Step 42). The values of opposite end portions of the block K are set as values of traffic information in extension ranges generated outside the block respectively (Step 43). Orthogonal transform described in the <Orthogonal Transform Encoding Process> is carried out on traffic information in a to-be-encoded traffic information range including the extension ranges (Step 44). This process is repeated all over the blocks of the traffic information (Step 45 and Step 46).

[0111] The number Ma of pieces of data in the upstream extension range and the number Mb of pieces of data in the downstream extension range are added to parameter information of DWT data generated thus, as shown in Fig. 15.
(2) Out-of-Boundary Encoding System
In the out-of-boundary encoding system, as shown in Fig. 16, a to-be-encoded traffic information range (the range surrounded by the broken line) of an intended block K is extended to the outside of the range of the intended block K. Traffic information in adjacent blocks put in the extension ranges is used as traffic information of the to-be-encoded traffic information range of the intended block K

[0112] The flow chart of Fig. 17 shows the procedure of encoding in this system. First, the number M of blocks of traffic information to be provided is acquired (Step 50). Sequentially in order of increasing block number from the block number K=1 (Step 51), traffic information of the block K and traffic information of the extension ranges of the adjacent blocks are acquired (Step 52). Orthogonal transform is carried out on traffic information in the to-be-encoded traffic information range including the extension ranges (Step 53). This process is repeated all over the blocks of the traffic information (Step 54 and Step 55).

[0113] In the same manner as in the case of the boundary value extending system (Fig. 15), the number Ma of pieces of data in the upstream extension range and the number Mb of pieces of data in the downstream extension range are added to parameter information of DWT data generated thus.

[0114] (3) Window Function Usage System
A window function is a function having a maximum value of 1 and a minimum value of 0 and attenuated at its opposite ends so that a value obtained by adding the window function to another window function adjacent thereto is always 1 as shown in Fig. 18(b). Here, assume that a function used as a window function f(k) of an intended block K is a window function f(k) crossing a window function f(k-1) of an upstream adjacent block K-1 on the upstream boundary of the intended block K and crossing a window function f(k+1) of a downstream adjacent block K+1 on the downstream boundary of the intended block K, and traffic information of the to-be-encoded traffic information range of the intended block K is obtained by multiplying traffic information of the upstream adjacent block K-1, the intended block K and the downstream adjacent block K+1 by the window function fk.

[0115] The flow chart of Fig. 19 shows the procedure of encoding in this system. First, the number M of blocks of traffic information to be provided is acquired (Step 60). Sequentially in order of increasing block number from the block number K=1 (Step 61), traffic information of the block K and necessary traffic information of the adjacent blocks are acquired (Step 62). A value of traffic information at each sampling point of the traffic information is multiplied by a window function (Step 63), and subjected to orthogonal transform as traffic information of the to-be-encoded traffic information range (Step 64). This process is repeated all over the blocks of the traffic information (Step 65 and Step 66).

[0116] Window function definitions used for generating the traffic information of the to-be-encoded traffic information range are added to parameter information of DWT data generated thus, as shown in Fig. 20. Various window functions such as a trapezoidal window, a triangular window, a trigonometric function window, etc. can be used as the window function. Identification information of a window function used selectively from some window functions defined in advance is described in the parameter information.

[0117] The traffic information of each block subjected to the block noise reduction process and the orthogonal transform encoding in such a manner is sent to the data transmitting portion 18 together with the road shape data. Incidentally, the road shape data may be encoded with a variable length code by the variable length encoding process portion 18 so that the amount of data is compressed. The method of this variable length encoding has been described in detail in the aforementioned Japanese Patent Laid-Open No. 2003-23357.

[0118] The data transmitting portion 18 transmits this traffic information and the road shape data to the information use apparatus 40. The traffic information and the road shape data (road reference data) are received by the data receiving portion 41 which constitutes an acquisition portion for acquiring the traffic information transmitted from the information transmitting apparatus 10. Figs. 21 show data structures of the road shape data (a), the block marker information (b) and the traffic information (c) to be transmitted to the information use apparatus 40. The block marker information (b) includes the shape identification number of each target road included in the road shape data (a), the number of blocks of traffic information of the target road, the node numbers of nodes where block markers have been set, and distances between the block markers. Further, the traffic information (c) includes the shape identification number, the information category of traffic information, the number of blocks of the traffic information, the parameter information of each block shown in Fig. 12(a), Fig. 15 or Fig. 20, and the orthogonally transformed traffic information of each block shown in Fig. 12(b).

[0119] Incidentally, in the case where the road shape data are encoded by a variable length code, the effect of data compression is enhanced when the road shape data are encoded using only nodes set by equidistant resampling (provided that the resampling length of each road section is varied in accordance with the curvature of the section) without adding the block marker positions to the nodes. Therefore, in this case, each block marker position is expressed by a distance D1, D2, D3 from a left adjacent node set by equidistant resampling as shown in Fig. 22. When resolution required for identifying the distance D1, D2, D3 is d (m), the number of bits required for expressing the distance D1, D2, D3 can be obtained by:
number of required bits = roundup[log₂(L/d)]
when L is resampling length (m)
On the assumption that d=3 m (distance driven by a vehicle for about 0.1 second), 2 bits suffice when L is 10 m, 6 bits are required when L is 160 m, and 8 bits are required when L is 640 m. Fig. 23 shows the relationship between the resampling length and the number of bits required for expressing a node to block marker distance. Fig. 24 shows road shape data including position information of each node followed by identification code of a block marker and information (value D) of distance from the node.

[0120] The information use apparatus 40 having received the traffic information and the road shape data sends the road shape data and the block marker information to the encoded shape data decoding portion 42, and sends the traffic information to the encoded traffic information data decoding portion 48.

[0121] The encoded traffic information data decoding portion 48 acquires the orthogonal transform coefficients of each block and decodes block-by-block traffic information in the procedure shown in Fig. 25. The encoded traffic information data decoding portion 48 constitutes a reproducing portion (traffic information decoding portion) for decoding the traffic information block by block so as to reproduce sampled data.

[0122] The order N of DWT is read from the parameter information of the received traffic information (Step 70). The value n is set at N-1 (Step 71), and the number of pieces of input data is decided by (number of pieces of data)/2ⁿ (Step 72). Next, IDWT is performed by the filter circuit in Fig. 8(b) with the scaling coefficients in the front side of input data and the wavelet coefficients in the rear side of the input data, so that one-lower-order scaling coefficients are reconstructed (Step 73).

[0123] When n>0 or when it is within a time limit, the routine of processing returns to Step 72, where one is subtracted from the value n. The procedure of Step 72 and Step 73 is repeated (Step 74). When n=0 and IDWT is terminated, the data are inversely shifted in accordance with the level shift on the transmitting side, so that block-by-block traffic information is restored (Step 77). When it is beyond the limit time of the IDWT process, IDWT is terminated, and the time resolution is set to be 2ⁿ times in order to express traffic information with a reduced resolution using the obtained traffic information data (Step 76). Inverse shift is carried out to restore averaged block-by-block traffic information (Step 77).

[0124] When a block noise reduction process using a boundary value extending system or an out-of-boundary encoding system is carried out on the transmitting side, the block noise reduction process portion 49 extracts only information in the range of the intended block K from the restored values so as to obtain traffic information of each block. On the other hand, when a block noise reduction process using a window function usage system is carried out on the transmitting side, the restored values of the intended block K are added to the values of the block (K-1) restored before the intended block K, and this process is repeated to obtain traffic information of each block.

[0125] On the other hand, when the road shape data are encoded using a variable length code, the road shape data are decoded by the encoded shape data decoding portion 42, and restored by the shape data restoring portion 43.
The position identifying portion 44 performs position identification by which the target road expressed by the road shape data is identified on a map of the digital map database (B) 45.

<Distance Displacement Correction Process>

[0126] The blocking position identifying portion 46 calculates the latitude and longitude of each block marker position from the position of each node identified on the target road and the block marker information, so as to identify each block section. Figs. 26 show this process schematically. Fig. 26(a) shows road shape data generated using map data of the digital map database (A) 12 by the information transmitting apparatus 10 (here, block marker positions (BM1, BM2 and BM3) are set as nodes). Fig. 26(b) shows the state where node positions included in the road shape data are expressed on a map of the digital map database (B) 45 by the information use apparatus 40. The position identifying portion 44 performs position identification so as to position these nodes on a road in the digital map database (B) 45 as shown in Fig. 26(c). The blocking position identifying portion 46 calculates the latitudes and longitudes of the block marker positions (BM1, BM2 and BM3) positioned on this road based on the data of the digital map database (B) 45, so as to identify each block section.

[0127] The block-by-block correction coefficient calculating portion 7 calculates a distance (Bd) of each block along the road using the data of the digital map database (B) 45, and calculates a correction coefficient in this block from the ratio between this distance (Bd) and the distance between block markers in this block expressed based on the block marker information. When the distance transmitted from the information transmitting apparatus 10 is applied to the block, the distance has to be corrected by this correction coefficient.

[0128] The block-by-block unit distance correcting portion 50 corrects the length of the block included in the parameter information by the correction coefficient, and divides the corrected length by the number Na of pieces of data of the block (the number of divisions of the block) so as to obtain a distance between sampling points. Thus, the position of each sampling point included in the block whose position is identified by the blocking position identifying portion 46 is identified. Then, the data of the traffic information of this block are assigned to the respective sampling points so as to reproduce the traffic information.

[0129] Assume that the block markers disagree with the nodes as shown in Fig. 22. In this case, a distance N1 between a node n1 and a node n2 is calculated using distances D1 and D2 between block markers included in the block marker information, while a distance N2 along a road of the digital map database (B) 45 between the node n1 and the node n2 identified on the road is calculated. Thus, a correction coefficient is calculated from a ratio between N2 and N1. Then, the distances D1 and D2 are corrected by the correction coefficient. The block is identified so that a place at the corrected distance D1 from the node n1 is set as one boundary and a place at the corrected distance D2 from the node n2 is set as the other boundary.

[0130] When an accident occurrence position expressed by a distance from a reference node is transmitted, the block-by-block unit distance correcting portion 50 corrects the distance by the correction coefficient, and identifies, as the accident occurrence position, a place which is at the corrected distance from the reference node identified on a road of the digital map database (B) 45.

[0131] The traffic information superimposing portion 51 superimposes restored block-by-block traffic information sequentially on the target road. The information use portion 52 makes good use of this traffic information.
In such a manner, according to this method for generating traffic information, traffic information of a target road is divided into small blocks and encoded so that the load on a program can be reduced, and the memory size of a work memory to be used for processing such as encoding or decoding can be saved. Accordingly, an encoding/decoding portion can be constituted by a semiconductor chip or the like.

[0132] In addition, the compressibility of the traffic information can be varied for each small block, so that the fineness of the traffic information can be set in accordance with necessity.
In addition, the displacement in the distance direction of a road can be corrected using the positions of the boundaries among the blocks of the traffic information can be corrected so that high-precision information can be transmitted.

[0133] Further, the traffic information of each small block can be encoded or decoded more efficiently by a streaming process or a pipeline process in which an input block is processed and outputted before a subsequent block is input.

[0134] Incidentally, the traffic information may be sampled and divided into blocks in such a manner that the traffic information is sampled and the obtained sampled data are divided into a plurality of blocks, or the positions where the traffic information will be divided into blocks are decided before sampling, and sampling is then performed at predetermined intervals in each block.

<Modifications>

[0135] Description has been made about the case where the length of each block is set to be constant. However, traffic information may be blocked at a place where a traffic flow is apt to change (such as at a bottleneck crossing, before famous facilities, etc.). Fig. 27 shows an example in which block markers are set in famous crossings or bottleneck crossings. In this case, the distances between the block markers are not equal to one another. However, when the number of divisions (number Na of pieces of data) in each block is fixed or when the number Na of pieces of data is set in a range not larger than a predetermined maximum value, it is possible to attain the effect on reduction of the load on the encoding/decoding process, adaptive alteration of compressibility, and correction of displacement in the distance direction. In the case of this modification, the traffic situation between important crossings is expressed by one block of traffic information so that the traffic situation can be understood more easily. In addition, a block of traffic information to be reproduced can be selected on the information use apparatus side. Thus, for example, only the traffic situation between crossings for the information use apparatus side to want to know can be reproduced.

[0136] In addition, description has been made about the case where traffic information is divided and blocked by distance. However, when probe car on-vehicle equipment provides traffic information (measured information) to a probe information gathering center, the traffic information may be divided and transmitted by time. When the center provides traffic information about travel time, the traffic information may be blocked by travel time.

[0137] In addition, description has been made about the case where road shape data including a data array of node positions on a target road of traffic information are used to transmit the target road. However, as data (road section reference data) for identifying the target road, for example, an identification code added to a target road section in advance, a road section identifier (link number), and a crossing identifier (node number) defined by standards, etc. may be used.

[0138] When both the providing side and the receiving side refer to one and the same map, the providing side may provide latitude and longitude data to the receiving side so that the receiving side can use the data to identify each road section.
Further, a target road section of traffic information may be identified using identifiers added to tile-shaped divisions of a road map respectively, kilometer posts provided in roads, road names, addresses, zip codes, etc. as road section reference data.

(Second Embodiment)

[0139] In a second embodiment, there will be shown an example in which block markers are set desirably at non-equal intervals in the same manner as in the aforementioned modification in Fig. 27. This second embodiment is an embodiment preferred when a probe car is assumed as the information transmitting apparatus, and traffic information such as speed information etc, is gathered by the probe car.

[0140] Fig. 28 is a diagram schematically showing a first example and a second example as the method for generating traffic information according to the second embodiment. In the first example, based on an output of a vehicle sensor such as a steering angle sensor, a gyrocompass, etc. provided in a probe car, it is concluded that there has occurred an event when the moving direction of the probe car changes largely beyond a predetermined value, that is, when the moving probe car turns largely beyond a predetermined angle, and a block marker is set at this place. As shown in Fig. 28, assume that there is a crossing at a place 3,000 m to 4,000 m distant from a place where setting of block markers is started, and the probe car turns right at the crossing. Then, assume that congestion of vehicles waiting to turn right occurs short of this crossing point.

[0141] Such a place where the probe car turns largely can be regarded as a turning point of traffic situation such as a crossing. Accordingly, when a block marker is inserted here, the position where the traffic situation changes can be determined clearly even if the traffic information is compressed block by block. In addition, where there is a turning point of traffic situation such as a crossing is shown clearly by the block marker. Accordingly, when the waiting time to turn right/left (right/left turning cost) is calculated from gathered traffic information, the position of the crossing can be grasped clearly so that the accuracy of the waiting time to turn right/left can be improved. Also when congestion information is generated, the position of a break of a line of waiting vehicles, such as a congestion start position or a congestion end position, can be determined easily. Thus, it is easy to calculate the waiting time or the end position of the line of waiting vehicles.

[0142] The second example is another example using an output of a vehicle sensor, in which, based on an output of a vehicle sensor such as a speed sensor provided in a probe car, it is concluded that there occurs an event when the probe car has stopped for N or more minutes, and a block marker is set at this place. For example, a block marker is inserted when a stopping state has continued for three or more minutes. Typically, a signal control cycle is 45-180 seconds, and a stopping time to wait for the traffic light to change is about 20-90 seconds. The stopping time is up to about 180 seconds even when the probe car has been far from moving for 2 cycles due to clogging beyond the crossing. When the probe car has stopped for a time longer that this time, the probe car can be regarded as stopping out of a traffic flow, such as stopping due to passengers getting on and off a taxi, stopping for waiting for a person, or the like. Such a stop is not suitable as traffic information. Therefore, a block marker is inserted to expressly provide a place where there occurs an event of a stop. Thus, the position where the running state of the probe car has changed can be determined clearly so that highly reliable traffic information can be provided.

[0143] In the aforementioned first and second examples, when the compressibility of traffic information is changed between blocks before and after a block marker set at a place where there occurs an event of turning right at a crossing, stopping, or the like, traffic information having a suitable amount of information in each divided block can be generated. For example, the compressibility of an upstream block located short of a crossing is reduced to increase the amount of information and make the traffic information finer so that it can be made easier to grasp the tail of a line of waiting vehicles such as congestion of vehicles waiting to turn right.

[0144] Fig. 29 is a diagram schematically showing a third example and a fourth example as the method for generating traffic information according to the second embodiment. In the third example, based on map information of a navigation system provided in a probe car and the position of the probe car itself, it is concluded that there has occurred an event at a place where the probe car leaves a road, at a place of an entrance of POI (Point Of Interest) which is a to-be-identified place interesting a user, such as a car park, a store, amusement facilities or the like, a place where the probe car enters a private road or a road inside facilities etc., and a block marker is set at this place.

[0145] When a car enters POI, the car may leave a public road network, or may run into a private road or a road inside facilities. Typically, as for traffic information such as congestion information or the like, any other information than information about the public road network is not required. Therefore, a block marker is inserted at each place as mentioned above, so that a boundary place between the public road network and the others can be expressly provided. Thus, the positions where the car goes into/out of the public road network can be identified easily so that traffic information high in necessity can be provided. In the case where there occurs congestion of vehicles waiting to enter a car park or facilities, when congestion information is generated, the position of a break of a line of waiting vehicles, such as a congestion start position or a congestion end position, can be determined easily in the same manner as in the aforementioned first example. Thus, it is easy to calculate the waiting time or the end position of the line of waiting vehicles.

[0146] In the fourth example, based on information of communication apparatus such as DSRC (Dedicated Short Range Communication) system narrow-band radio communication apparatus provided in a probe car, it is concluded that there has occurred an event when communication takes place, and a block marker is set at this place. For example, a block marker is inserted when the probe car passes a gate of an ETC (Electronic Toll Collection) system using DSRC system narrow-band communication and provided in a tollgate of an expressway or the like, or when data transmission/reception takes place in a DSRC system provided in an entrance of a car park or facilities.

[0147] Also in an interchange entrance/exit road or the like located near a tollgate or connected to the tollgate, a traffic situation changes due to congestion in the tollgate or the like. Also in an entrance of a car park or facilities, a traffic situation may change due to congestion of vehicles waiting to enter the car park or facilities. A block marker is inserted at such a place so that the position where the traffic situation changes can be determined clearly. In addition, the place of the entrance of POI or the like can be determined clearly, or a public road network can be distinguished clearly from the other places such as the inside of POI or the like. Thus, useful traffic information can be provided.

[0148] Fig. 30 is a block diagram showing the configuration of information transmitting apparatus 110 for providing traffic information according to the second embodiment, and the configuration of information use apparatus 40 for making good use of the provided traffic information. This information transmitting apparatus 110 is probe car on-vehicle equipment in which the configuration of the information transmitting apparatus 10 according to the first embodiment shown in Fig. 2 is modified partially. Incidentally, in Fig. 30, constituent parts similar to those in Fig. 2 are denoted by the same reference numerals correspondingly, and detailed description thereof will be omitted.

[0149] The information transmitting apparatus 110 has a GPS position detecting portion 121, a speed sensor 122 and a gyrocompass 123 as vehicle sensors. In addition, the information transmitting apparatus 110 has a running trajectory measured information input portion 111 for importing map information of digital map database (A) 12 and information measured by the respective vehicle sensors, and inputting them as running trajectory measured information of a probe car, a running trajectory shape extracting portion 113 for generating shape data of a running trajectory of the probe car with respect to a target road or POI of traffic information from output information of the running trajectory measured information input portion 111, a measured information blocking determining portion 114 for determining the divided positions of measured information to be blocked based on output information of the aforementioned running trajectory measured information input portion 111, the digital map database (A) 12 and the respective vehicle sensors, and generating block-by-block traffic information, and a block position marker adding portion 115 for adding block markers to the shape data of the running trajectory based on output information of the aforementioned running trajectory shape extracting portion 113 and the aforementioned measured information blocking determining portion 114, In addition, information from a steering angle sensor 124 and information from a DSRC communication portion 125 are designed to be input to the measured information blocking determining portion 114.

[0150] The information transmitting apparatus 110 constitutes an encoder from the point of view of generation of encoded data, while the information use apparatus 40 constitutes a decoder from the point of view of restoration of the encoded data.
A block marker setting process in the information transmitting apparatus 110 configured as mentioned above is performed in the procedure shown in Fig. 31. Fig. 31 is a now chart showing a procedure to add biock markers to probe car measured information in the second embodiment.

[0151] Measurement of speed etc. by the probe car is repeated every unit time (or at a fixed distance interval), and measured data are accumulated in a buffer (Step 101). When it is time to transmit probe information (Step 102), the measured information blocking determining portion 114 decides the unit with which each block marker will be added (Step 103). Here, the unit with which each block marker will be added is, for example, set to be a value fixedly decided in the system or a value decided based on measurement of a current free memory capacity of the buffer. Incidentally, two kinds, that is, a fixed distance unit and a fixed time unit can be considered as the unit. Initially, the node number N of road shape data of a target road is set at 1 (Step 104). Information from the running trajectory measured information input portion 111, the digital map database (A) 12 and the respective vehicle sensors of the GPS position detecting portion 121, the speed sensor 122 and the gyrocompass 123 are input, and it is determined whether there occurs a predetermined event in the node N or not (Step 105).

[0152] Here, as described in the aforementioned first to fourth examples, examples of such predetermined events include (1) the case where it is concluded that the probe car "has tumed at a large angle" based on the outputs of the vehicle sensors (steering angle, gyrocompass, GPS direction, etc.), (2) the case where it is concluded that the probe car "has stopped for a predetermined time or longer" based on the outputs of the vehicle sensors (speed etc.), (3) the case where it is concluded that the probe car "has left the road", "has entered the entrance of POI (car park or the like) or "has entered a private road or a road inside facilities" based on the result of position identification of shape data of the running trajectory, or it is concluded that the probe car is at a traffic important place such as at a main crossing, in front of large-scale facilities or the like, (4) the case where communication with an ETC system or a DSRC system has took place based on information from a DSRC communication portion, and so on.

[0153]  When there occurs a predetermined event (Yes in Step 106), the measured information blocking determining portion 114 sets a block marker in the place where this event occurs, and generates block marker information (Step 107). Then, it is determined whether the distance or time interval from the last position where a marker was set is or not beyond the decided unit with which a block marker will be added (Step 108). On the other hand, when no event occurs in Step 106, no block marker is generated in Step 107, but determination about the unit is performed in Step 108. Then, when the interval is beyond the unit (Yes in Step 109), block marker information is generated by fixed unit with which a block marker will be added (Step 110). After that, it is determined whether processing all over the nodes of the road shape data of the target road is terminated or not (Step 111). On the other hand, when the interval is not beyond the unit, it is determined whether processing all over the nodes is terminated or not, without generating a block marker in Step 110.

[0154] When the process to determine whether to insert a block marker and generate the block marker is not terminated all over the nodes of the road shape data of the target road, the node number N is increased to N+1 by one (Step 112), the routine of processing returns to Step 105 so as to repeat the processing of Steps 105-110 for the next node. On the other hand, when processing all over the nodes is terminated, the compressibility of traffic information is decided by the block-by-block compressibility deciding portion 16 for each block to be divided by the block markers generated by the measured information blocking determining portion 114. After a block noise reduction process is performed by the block noise reduction process portion 17, an orthogonal transform encoding process such as DWT is performed block by block by the orthogonal transform encoding process portion 19 so as to compress the data (Step 113). In addition, the block position marker adding portion 115 adds position information of block markers to the shape data of the running trajectory generated by the running trajectory shape extracting portion 113, based on the block marker information generated by the measured information blocking determining portion 114 (Step 114).

[0155] When traffic information is divided into small blocks and compressed block by block, measured information such as speed or travel time per unit section is averaged due to compression. Accordingly, when the compressibility is increased, it is difficult to determine a turning point of a traffic situation. Thus, it may be difficult to determine the position of an end portion of that event when congestion information or the like is generated. Therefore, in the second embodiment, when there occurs an event corresponding to a turning point of a traffic situation such as turning right/left at a crossing or entering POl, a block marker is set in a position corresponding to this event so that the turning point of the traffic situation can be determined easily, In addition, a suitable and efficient compression process can be performed on each of the blocks divided by such block markers. Thus, saving of the amount of data of traffic information and the improvement of usability thereof can be made compatible.

[0156] Although the present invention has been described in detail and with reference to its specific embodiments, it is obvious for those skilled in the art that various changes or modifications can be made on the present invention without departing from the spirit and scope of the present invention.

[0157] The present application is based on a Japanese patent application (Japanese Patent Application No. 2003-360630) filed on October 21, 2003 and a Japanese patent application (Japanese Patent Application No. 2004-118744) filed on April 14, 2004, and their contents are incorporated herein by reference. Industrial Applicability

[0158] The method for generating traffic information according to the present invention can reduce a load on software and hardware on the side where the traffic information is generated and on the side where the traffic information is used. The method can be used broadly when traffic information, probe information, etc. are generated for transmitting, recording or the like.

[0159] The apparatus according to the present invention is applicable to center apparatus of a traffic information providing system, probe car on-vehicle equipment for providing measured information, and so on. In addition, the apparatus is broadly applicable to center apparatus for gathering probe car information, or an information terminal such as a car navigation system, a personal computer, a PDC, a cellular phone, etc., as apparatus on the side where information is used.

Claims

1. A method of generating traffic information in which a traffic situation of a target road is sampled at predetermined intervals along the road, comprising the steps of:

dividing an array of sampled data into a plurality of blocks; and

encoding the sampled data included in the blocks by orthogonal transform block by block.

2. A method of generating traffic information according to claim 1, wherein the number of pieces of the sampled data included in each of the blocks is set to be not larger than a predetermined upper limit number.

3. A method of generating traffic information according to claim 2, wherein the number of pieces of the sampled data included in each of the blocks is set to be fixed.

4. A method of generating traffic information according to any one of claims 1 to 3, wherein the target road is divided into sections at constant distance intervals, and the blocks are generated correspondingly to the divided sections.

5. A method of generating traffic information according to any one of claims 1 to 3, wherein the target road is divided into sections at non-equidistant intervals with selected places set as boundaries, and the blocks are generated correspondingly to the divided sections.

6. A method of generating traffic information according to claim 5, wherein places of crossings or facilities are selected as the boundaries.

7. A method of generating traffic information according to any one of claims 1 to 3, wherein the sampled data are divided by time to generate the blocks.

8. A method of generating traffic information according to any one of claims 1 to 3, wherein in the case that the sampled data are measured information measured by probe car on-vehicle equipment, the measured information is divided into a plurality of pieces by time zone of measuring time, and the blocks are generated in accordance with the divided pieces of the measured information.

9. A method of generating traffic information according to any one of claims 1 to 3, wherein in the case that the sampled data are measured information measured by probe car on-vehicle equipment, block markers indicating boundaries between the blocks are set based on at least one of running information in the probe car on-vehicle equipment, position information on map information where a position of the probe car on-vehicle equipment is associated, and communication operation information in a communication portion mounted on the probe car on-vehicle equipment.

10. A method of generating traffic information according to claim 9, wherein the block markers are set when predetermined events occur during travel of the probe car on-vehicle equipment based on at least one of the running information, the position information and the communication operation information.

11. A method of generating traffic information according to any one of claims 1 to 10, wherein data compressibility in encoding is set block by block.

12. A method of generating traffic information according to claim 11, wherein the data compressibility is changed in accordance with an average speed in the blocks expressed by the sampled data.

13. A method of generating traffic information according to claim 11, wherein the data compressibility is changed in accordance with a rate of change in average speed of the blocks expressed by the sampled data between adjacent ones of the blocks.

14. A method of generating traffic information according to claim 11, wherein the data compressibility is changed in accordance with an event occurring in a section corresponding to each of the blocks.

15. A method of generating traffic information according to claim 11, wherein the data compressibility in each block including measured information of the probe car on-vehicle equipment as the sampled data is changed in accordance with an event measured by the probe car on-vehicle equipment.

16. A method of generating traffic information according to claim 11, wherein the data compressibility in each block including measured information measured by the probe car on-vehicle equipment as the sampled data is changed in accordance with measuring time at which the probe car on-vehicle equipment measures the measured information.

17. A method of generating traffic information according to claim 11, wherein the data compressibility in each block including measured information measured by the probe car on-vehicle equipment is changed in accordance with whether a measuring place is near a specified position or not.

18. A method of generating traffic information according to claim 1, wherein in encoding block by block, a range of each of the blocks is extended, and encoding is performed on sampled data of the block including sampled data of an extension portion thereof.

19. A method of generating traffic information according to claim 18, wherein values of the sampled data in the extension portion are brought into agreement with values of sampled data at an original boundary of the block.

20. A method of generating traffic information according to claim 18, wherein values of sampled data in the extension portion are brought into agreement with values of corresponding sampled data of a block adjacent to the block.

21. A method of generating traffic information according to claim 18, wherein values of sampled data in the extension portion are brought into agreement with values of corresponding sampled data of a block adjacent to the block, the sampled data of the block including the extension portion are multiplied by a window function, and values obtained thus are set as sampled data of the block.

22. A method of generating traffic information according to claim 1, wherein position information indicating boundaries between the blocks is added to road reference data for specifying the target road, so as to be a part of the traffic information.

23. A method of reproducing traffic information in which a traffic situation of a target road is sampled at predetermined intervals along the road, comprising the steps of:

acquiring traffic information generated by dividing an array of sampled data into a plurality of blocks and encoding the sampled data block by block; and

decoding the traffic information block by block so as to reproduce the sampled data.

24. A method of reproducing traffic information according to claim 23, wherein in reproducing the sampled data, the traffic information is associated with position information and output.

25. A method of reproducing traffic information according to claim 23, wherein in reproducing the sampled data, the traffic information is associated with position information and displayed on a display portion.

26. A program of making a computer execute respective procedures of a method for generating traffic information according to any one of Claims 1 to 22.

27. A program of making a computer execute respective procedures of a method for reproducing traffic information according to any one of Claims 23 to 25.

28. An apparatus of generating traffic information in which a traffic situation of a target road is sampled at predetermined intervals along the road, comprising:

a block dividing portion for dividing an array of sampled data corresponding to the traffic situation into a plurality of blocks; and

an encoding portion for encoding the sampled data included in the blocks by orthogonal transform block by block.

29. An apparatus for generating traffic information, comprising:

a traffic information blocking portion for dividing an array of sampled data into a plurality of blocks, a traffic situation of a target road having been sampled in the sampled data;

a block-by-block compressibility deciding portion for deciding compressibility in encoding the sampled data included in each of the blocks;

a block noise reduction process portion for performing a process for reducing block noise generated in boundaries between the blocks in decoding; and

an orthogonal transform encoding process portion for encoding the sampled data in the blocks, subjected to the block noise reduction process, by orthogonal transform block by block.

30. An apparatus for generating traffic information according to claim 29, further comprising:

a block position marker adding portion for adding position information of block markers to road reference data specifying the target road, the block markers indicating boundaries between the blocks,

wherein the apparatus provides the encoded data generated by the orthogonal transform encoding process portion and the road reference data added with the position information of the block markers.

31. An apparatus for generating traffic information according to claim 30, wherein the block position marker adding portion divides the target road into sections at predetermined distance intervals, and sets the block markers correspondingly to the divided sections.

32. An apparatus for generating traffic information according to claim 30, wherein in the case that the sampled data are measured information measured by probe car on-vehicle equipment, the block position marker adding portion divides the measured information into pieces at predetermined time intervals, and sets the block markers correspondingly to the divided pieces of the measured information.

33. An apparatus for generating traffic information according to Claim 30, wherein in the case that the sampled data are measured information measured by probe car on-vehicle equipment, the block position marker adding portion sets the block markers based on at least one of running information in the probe car on-vehicle equipment, position information on map information where a position of the probe car on-vehicle equipment is associated, and communication operation information in a communication portion mounted on the probe car on-vehicle equipment.

34. An apparatus for reproducing traffic information in which a traffic situation of a target road is sampled at predetermined intervals along the road, comprising:

an acquiring portion for acquiring traffic information generated by dividing an array of sampled data corresponding to the traffic situation into a plurality of blocks, and encoding the sampled data biock by block; and

a reproducing portion for decoding the traffic information block by block so as to reproduce the sampled data.

35. An apparatus for reproducing traffic information, comprising:

a receiving portion for receiving traffic information in which sampled data indicating a traffic situation of a target road is divided into blocks and the sampled data is encoded block by block, and road reference data indicating the target road and boundary positions between the blocks;

a traffic information decoding portion for decoding the traffic information block by block so as to reproduce the sampled data;

a block noise reduction processing portion for excluding sampled data which is added thereto in order to reduce block noise, from the reproduced sampled data, and acquiring sampled data included in a range of each of the blocks;

a block-by-block correction coefficient calculating portion for calculating correction coefficients for correcting a displacement occurring in a distance direction of the target road by use of information of boundary positions between the blocks included in the road reference data; and

a block-by-block unit distance correcting portion for identifying a correct position of each of the blocks on the target road by use of the correction coefficients, and positioning the sampled data in sampling positions of the block.

Drawing