(19)

(11)

EP 0 409 863 A1

(12)

(43) Date of publication: 30.01.1991 Bulletin 1991/05 (21) Application number: 89904152.0 (22) Date of filing: 23.02.1989

(51) International Patent Classification (IPC):  G01V 1/ 20( . ) (86) International application number: PCT/GB1989/000186 (87) International publication number: WO 1989/008270 (08.09.1989 Gazette 1989/21)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 24.02.1988 GB 19880004314 (71) Applicant: WYATT, Roy Lee-on-Solent, Hampshire (GB)	(72) Inventor: WYATT, Roy Lee-on-Solent, Hampshire (GB) (74) Representative: Lomas, Geoffrey Michael, et al  Barker, Brettell & Boutland Prudential Buildings 97-101 Above Bar Street Southampton SO9 4GT Southampton SO9 4GT (GB)