Tony writes “I managed to write a perl script to do the Garmin GPS Overlay on an arbitrary satellite image. You can get ridiculously high resolution, color satellite orthoimages from seamless.usgs.gov, and then overlay the tracks on the image with PerlMagick. My PerlMagick script to do this is here“. I use the same GPS Tony has, the Garmin Forunner- nice work! Link.
PerlMagick+Garmin GPS Data+USGS Orthoimages