Gentleman
There is a program available called SH3 gen
This will read your SCR and RND and plot information on your map - you can choose the level of intel you want with a slider
You will then have a nav map marked with minefields and subnets ane information about what ships may be in any particular harbour
Great tool that works with any mod
http://www.global-explorer.de/
You can take it as cheating or take it that its information relayed back to BDU from other boats that have been in a particular area