I'm afraid all this stuff is hard coded in the .exe files. Modding those isn't modding, it's illegal hacking, so you have two choices as a modder.
Choice 1 is to turn off the sub position symbol on the nav map and attack map, find the sub position in the game files and feed that to an exterior planetarium file. That's what has been done by the navigation mod people for SH4. In doing so you give up a ton of realistic and useful things......like the ability to attack and sink opponents. This is not a workable scheme to my way of thinking other than as a proof of concept and a navigation trainer.
Choice 2 is not to do celestial navigation in SH4. That's been my path.
Or you could go to door #3 where the object of the game seems to be walking around your sub asking how the soup is for the ten thousandth time to build morale, while playing a bizarre Frankenstein poorly executed submarine meets horrible parody of the Sims monster. I'll pass on that one too. I could care less if Johan's girlfriend is pregnant with kittens.
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