Question

I don’t mind writing XSL but if one has already been written I should reuse it.

rtept = route point in the GPX format
trkpt = track point in the GPX format

Converting latitude and longitude points from the first to the second, ignoring irrelevant elements.

Answer 1

Unless someone proves me wrong, there is no such XSL application available.

I would have loved to contribute one, but incidentally the whole point of the conversion disappeared when I discovered that GMapToGPX can generate files in the trkpt format directly.