QLandkarte GT is the ultimate outdoor aficionado's tool. It supports GPS maps in GeoTiff format as well as Garmin's img vector map format. Additional it is the PC side front end to QLandkarte M, a moving map application for mobile devices.
Multiplatform Ham Radio APRS and Mapping Program
NOTE: Code commits are FROZEN on SourceForge: New code is now at <http://github.com/Xastir/Xastir>. Real-time tracking & messaging of stations via radio/internet APRS data streams, w/125 map formats supported. Linux/FreeBSD/Solaris/MacOSX/Windows in any of 7 languages. Can also be used for mobile mapping w/GPS. MAILING LISTS ARE AT: PROJECT->WEB SITE.
RouteConverter is another route conversion tool. It helps me and I hope it could help you.