I have Garmin 24K TopoMaps for the West and Southwest. When in Basecamp I can see topo lines for only one at a time. How can I merge them to see both at once? I live in Mesquite, NV which in on the border of the two maps.
You can't merge maps. You can have many topo maps active at the same time, but if there is any overlap at state borders between the two maps you will only see one or blank space. This is probably what you are seeing. Pan 30-40 miles away into either state to see if this is the case.
The only workaround is to activate/deactivate each map sequentially on your unit as you cross the border. It sucks, I know.....I was dealing with this constantly when I was in Death Valley this Spring. OR, get the 100K Topo and use that when close to state borders.
