(19)

(11)

EP 0 932 817 A1

(12)

(43) Date of publication: 04.08.1999 Bulletin 1999/31 (21) Application number: 97943997.0 (22) Date of filing: 02.10.1997

(51) International Patent Classification (IPC):  G01C 19/ 56( . ) G01C 19/ 58( . ) (86) International application number: PCT/GB1997/002713 (87) International publication number: WO 1998/017973 (30.04.1998 Gazette 1998/17)

(84) Designated Contracting States: DE ES FR GB IT SE (30) Priority: 21.10.1996 GB 19960021873 (71) Applicant: BTG INTERNATIONAL LIMITED London SE1 6BU (GB)	(72) Inventor: COOPER, George London SE13 5AW (GB) (74) Representative: Bingham, Ian Mark  British Technology Group Ltd., 10 Fleet Place London EC4M 7SB London EC4M 7SB (GB)