Just wanna say welcome before I read your post!! It looks interesting from what I see so far.
I'll post ther rest of my comments after I read it.
EDIT: I have heard of this before in regards to targeting so no I don't think you are the first mate, but nevertheless you did a great job of explaining it! You could also do this while submerged while looking through the scope (which of course, is ideal
). Just will take a few more steps. You will be able to find the range and the bearing through that, just like the watcheman, but will have to do manually.