The map card doesn't know anything. GPS is what does the locating. If the body of water is on the map card, GPS will have it displayed when you are there unless you prevent it from doing that.
What sonar/GPS equipment do you have?
Edited by Wayne P. (12/04/17 08:11 PM)
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1