For a few months I've been making simple "trackmaps" of artificial reefs and other side-scanned bottom structure and selling them to local anglers. I've got the technical side of things dialed in on Lowrance. (I merge shapefiles into a single line in QGIS, save as GPX, set the trackcolor attribute using a Lowrance emulator, and save my whole map as a single USR track. I'm not worried about piracy at the moment.)

Humminbird is a little more trouble, but I'm making progress.

But Garmin Marine units are really kicking my butt. I don't know anyone who owns one, so every test means a drive to West Marine with a pocket full of SD cards. And, frankly, they're getting tired of me not buying anything. :)

Do any of you folks have a recommendation for the simplest way to display a shapefile line on Garmin Marine units? I'd like to avoid building an entire basemap from scratch, just to overlay a few structure tracings. I am open to suggestions though, because it seems like half the fishermen around here use Garmin equipment.

I'll attach a couple examples of my stuff in GPX and USR format so you can see what I'm going for.

Much thanks!