You buy a depth finder you purchase a maps sd for it. I'm trying to figure out the upgrade, I understand improvements ramps,
Docks marinas above water development.

When I think of a underwater characteristic, such as a contour change channels
Foundations bridges an the like how do u upgrade something that was there when u bought the map to start with.

Or does upgrade just pertain to new lakes not offered when u purchased the maps program thanks.

On Dale I see garmin maps boat from time to time also a large deep vee hull with Map Surveyor wrapped boat

Thanks