TWoS real Navigation?
 

How does this differ exactly from the stock retail game navigation and/or does TWoS Mod already alter or add to the stock navigation even before TWoS Real Navigation is applied?

Thanks!

Stock game circles your sub on the map 100% of the time and allows you to use the waypoint tool where you can plan out several waypoints in advance. Real navigation doesn't.

In RN you can ask your navigator crew to plot your position by dead reckoning or celestial method on demand which makes map marks which are also subject to some inaccuracy.