@P_Funk
Thank you very much for the kind words. They give me the strength to continue when I hit the dead ends or sometimes feel like I'm out of options. I am enjoying the challenge of learning how navigation works in real life, and also how it can be implemented in this game. It is amazing how much detail the developers put into this old game, and it is amazing what modders keep discovering about what they can do with it. SH3 is proving hard to kill.
I downloaded those documents and am reading with interest. I will be posting soon on the plan for the 3rd voyage of U-13. I can tell you now that it will focus on the sunrise and sunset times, and that I will drive the accuracy of predicted SR/SS times from the current many minutes of error to a more than reasonable few seconds of error.