(19)

(11)

EP 0 221 127 A1

(12)

(43) Date of publication: 13.05.1987 Bulletin 1987/20 (21) Application number: 86902876.0 (22) Date of filing: 08.05.1986

(51) International Patent Classification (IPC):  G01S 7/ 491( . ) G01S 17/ 58( . ) (86) International application number: PCT/GB1986/000246 (87) International publication number: WO 1986/006845 (20.11.1986 Gazette 1986/25)

(84) Designated Contracting States: GB (30) Priority: 10.05.1985 GB 19850011866 (71) Applicant: PA Consulting Services Limited London SW1X 7LE (GB)	(72) Inventors: GARDNER, Keith Foxton Cambridge (GB) STOREY, Philip, Adrian Cambridge (GB) ECCLESTONE, Ralph, Edward Cambridge (GB) (74) Representative: Nash, Keith Wilfrid, et al  KEITH W. NASH & Co. Pearl Assurance House 90-92 Regent Street Cambridge CB2 1DP Cambridge CB2 1DP (GB)