Cetus gps is the swiss army knife of gps tracking and field data collection. It is intended for use by gis surveyors, scientists, explorers and gps enthusiasts who need to extend the features of their standard gps equipment. Cgpsmapper creates maps click here for garmin units. Chartplotter is a java based moving map program for use with gps units that support the nmea communication protocol (the gpgll sentence). Clew is a freeware gps chart plotting program.