No good trail maps for Garmin? in GPS technology and devices Posted August 17, 2007 I've looked into publicly-available GIS sources for trails for creating my own maps. There is some data out there, Sorry for the rant. Anyone have any thoughts/suggestions/volunteering? That's the reason that comprehensive maps don't exist. If you have the data globalmapper can probably read the format the data is in, then you use cgpsmapper to generate the map. Getting the data is the hard part.