I can’t imagine there would be much practical knowledge in a generic course on GPS or any other form of electronic navigation. I have used
Garmin,
Raymarine and
Furuno in the last few years and in the distant past have been trained on Doppler,
Loran A,
Loran C, Omega and INS.
The first three are popular modern systems and all have their own advantages, disadvantages, idiosyncrasies, drawbacks and user unfriendliness. In my opinion none would lend themselves to book or classroom
learning without a lot of practical on-ocean usage.
I suspect the RYA GPS material is either ridiculously basic or so glommed up with advanced mathematics (as I suspect the British would do) as to be useless. You don’t need an intimate knowledge of spherical and analytic trigonometry any more to navigate. Load Open
Captain on your
laptop along with a few
charts and play with it. You’ll learn good practical knowledge, then graduate to one of the commercially available systems that you will actually be using and
work it backward and forwards (on the
water, underway) until you know and understand every detail.
I also highly recommend you have a working knowledge of
celestial navigation, not to mention DR, when all this electronic crap is rendered useless by Kim Jung Un.