Ultimate outdoor aficionado's tool for GPS maps in GeoTiff

QLandkarte GT
Free
Offline
http://www.qlandkarte.org/index.html

QLandkarte GT is the ultimate outdoor aficionado's tool for GPS maps in GeoTiff format as well as Garmin's img vector map format. Additional it is the PC side frontend to QLandkarte M, a moving map application for mobile devices. And it fills the gap Garmin leaves in refusing to support Linux. QLandkarte GT is the proof that writing portable applications for Unix, Windows and OSX is feasible with a minimum of overhead. No excuses!