Will the Garmin Oregon load gpx files from the microSD card?
Yes. Create a directory called [OR SD drive]:\Garmin\GPX and place the gpx files there. On the CO, gpx files loaded from the SD card were handled differently from those stored in internal memory. The gpx files on the SD card were loaded every time the Colorado started. This had two effects 1) all tracks, routes and waypoints would be reloaded even if they have been deleted on the Colorado and 2) large gpx files like pocket queries would be reloaded and slow down the startup process. This does not seem to be the case any longer.
