I've had a Garmin GPS for at least a decade and I've only run Basecamp once. I'm certain there are complicated ways to load a custom map onto your GPS using Garmin Basecamp. Doing this will give you a blank map with just the GPS tracks, a quick and dirty way to make an trail overlay from a bunch of separate GPX tracks. An easy way to do this is to select an unsupported map (like Google Satellite) on the first page, before you choose Download KMZ file. Tip: Sometimes I want the tracks from the Caltopo map, but no background at all. Whatever you rename the file is the name that will show up in the Custom Maps selection on the GPS later. something like 'ArcGIS_Topo.kmz') After you download the file, rename it to something that identifies the map and makes sense to you: in this case I'd probably rename the map as LakeChaplain.kmz. The file will have a name that incorporates the base layer (i.e. Once you have positioned the box the way you want, download the map from Caltopo by clicking the 'Download KMZ' link on the left side. (Google satellite images are not available, but if you want a sat image USTopo Imagery might do it for you. You can choose the type of map you want using the menu at the upper right hand screen corner. (You may have to zoom out first, after I did that, I was able to do this with both Chromium and Firefox.) You are able to adjust the size of the box with the drag handles in the corners, as well as move the box by grabbing the center dot. At the top of the screen, under the Print menu, select 'Download KMZ file' The red box is the area that the map will cover. For demonstration, you can use one of my Caltopo maps as a sample.

Gpx and kmz file garmin custom maps