NAVIGATIONAL, POSITION FINDING AND DIRECTION FINDING APPARATUS, NAMELY, A SATELLITE NAVIGATIONAL SYSTEM, A GLOBAL POSITIONING SYSTEM (GPS) AND PARTS THEREFOR, NAMELY, NAVIGATIONAL ELECTRONIC UNITS FOR THE DETERMINATION, STORAGE AND RETRIEVAL OF LONGITUDE AND LATITUDE AND PROJECTION COORDINATE READINGS; AND DIGITISER PADS AND COORDINATE INPUT DEVICES THEREFOR, FOR INPUTTING USER SELECTED NAVIGATIONAL DATA