(19)

(11)

EP 0 420 890 A1

(12)

(43) Date of publication: 10.04.1991 Bulletin 1991/15 (21) Application number: 89906811.0 (22) Date of filing: 16.06.1989

(51) International Patent Classification (IPC):  G01C 21/ 26( . ) G01S 5/ 00( . ) G01S 1/ 12( . ) (86) International application number: PCT/GB1989/000673 (87) International publication number: WO 1989/012835 (28.12.1989 Gazette 1989/30)

(84) Designated Contracting States: AT BE CH DE FR IT LI LU NL SE (30) Priority: 17.06.1988 GB 19880014456 (71) Applicant: BROWN, Keith, Chisholm Middlesborough TS1 5JT (GB)	(72) Inventor: BROWN, Keith, Chisholm Middlesborough TS1 5JT (GB) (74) Representative: Orr, William McLean  URQUHART-DYKES & LORD 8th Floor, Tower House Merrion Way Leeds West Yorkshire, LS2 8PA Leeds West Yorkshire, LS2 8PA (GB)