[Karl-Heinz Jaeger]

The map contact info setting refers to ships being displayed automatically on the nav map when your watch crew spots something. Every time you spot a ship, a black square representing it is displayed automatically on the navigation map.

Also when you are submerged and your hydrophone operator detects a contact, the nav map displays a black or red line along the bearing of the sound contact depending if it's a warship or a merchant. With map contact info switched off you don't get diddly appearing on the nav map either whn you spot a ship on the surface or hear a sound contact while submerged, forcing you to mark the position of any ship you see manually in order to keep track of it.

Good luck at 100% realism! Not quite there yet myself, still going as far as I can on my 78% career before starting at full realism. Let us know how you get on.