Trying to figure out a way to make contacts disappear in periscope view

[james_nix]

On the map I mean. So if I am on the surface map contacts will be there, but if I submerge, they will disappear. I have an idea that would simulate the tracking party on the surface, but since only you can see with the periscope they would be removed from the map.

I play with the subsensors sim file with sensor depth, my theory would be that the visual sensor (periscope) wouldn't activate until a certain depth but that didn't work. Any ideas?