How to determine the Long. & Lat. to change the 'Start at Sea' position?

[Squalus_]

Hey guys,

As the title says, how do I find the longitude and latitude of any given position on the map to change the 'Start at Sea' option in SH3 Commander?

I made a test save in a position I would like to use but found nothing helpful in the save files. The only values I found were the default used by Commander for Kiel.

Do I need to find the values from the Prime Meridian and Equator in-game?

Thank you!