GPSBabel - convert, upload, download data from GPS and Map programs
GPSBabel converts waypoints, tracks, and routes between popular GPS receivers such as Garmin or Magellan and mapping programs like Google Earth or Basecamp. Literally hundreds of GPS receivers and programs are supported. It also has powerful manipulation tools for such data. such as filtering duplicates points or simplifying tracks. It has been downloaded and used tens of millions of times since it was first created in 2001, so it's stable and trusted. By flattening the Tower of Babel that the authors of various programs for manipulating GPS data have imposed upon us, GPSBabel returns to us the ability to freely move our own waypoint data between the programs and hardware we choose to use. It contains extensive data manipulation abilities making it a convenient for server-side processing or as the backend for other tools.