(19)

(11)

EP 1 078 221 A1

(12)

(43) Date of publication: 28.02.2001 Bulletin 2001/09 (21) Application number: 99922262.3 (22) Date of filing: 17.05.1999

(51) International Patent Classification (IPC)7: G01C 15/00 (86) International application number: PCT/GB9901/361 (87) International publication number: WO 9960/335 (25.11.1999 Gazette 1999/47)

(84) Designated Contracting States: AT CH DE ES FR GB IT LI NL (30) Priority: 15.05.1998 GB 9810405 (71) Applicant: Measurement Devices Limited Aberdeen AB23 8EW (GB)	(72) Inventor: BALL, Stephen Leslie By Banchory AB31 6LL (GB) (74) Representative: Allan, James Stewart et al Murgitroyd & Company,373 Scotland Street Glasgow G5 8QA Glasgow G5 8QA (GB)