I've been thinking about this (probably too much) and I realized that you were partially correct in your original post, Aaronblood...
The concept I presented is still correct: The intersecting line that produces equidistant segments will give away the ship's course (and range if you have enough data)
BUT .... (and here's the part where you were correct) the way you find that line will not be the same as if you're sitting still. You can't just move the first reading over then draw intersecting lines... it's more complicated than that for dynamic data.
I have to look into it further to see if there's a way to find that magical line with equal segments with data taken while you're moving.
Thanks for second-guessing me on it and making me think about it more.
Back to the drawing board...