ThisworkhasoriginallybeendoneintheP.R.China(WuhanTechnicalUniversityofSurveyingandMapping)andinHongKong(ChineseUniversityofHongKong).Prof.LinHuigaveusefuladvice.Mr.HanHaiyang,andMs.ChenLilihelpedworkwiththeimplementationofprototypesystem.WealsothanktheSwissNationalScienceFoundationforitsfinancialsupportandacknowledgethecommentsofDr.AndreasGeppertandProf.KlausR.Dittrichonanearlierversionofthispaper.
