No chart is infallible. Every chart is liable to be incomplete, either through imperfections in the survey on wh ich i t is based, or through subsequent alterations to the topography or sea floor. However, in the vicinity of recognized shipping lanes charts maybe used with confidence for normal navigational needs. The mariner must be the f inal j udge of the reliance he can p lace on the information given, bearing i n mind his particular circumstances , safe and prudent navigatio n , local pilotage guidance and the judicious use of ava i lable navigational a i ds