is gps measured ground speed better than nothing in case of loss of ASI
This being PPRuNe many people haven't taken the trouble to either read or understand the question but once you have done so it is self-evident that the answer must be "Of course it is".
Anything is better than nothing. Sticking your hand out of the window and feeling the air is
better than nothing.
Of course there are caveats as gven above and GPS may well not be the
best way to handle loss of ASI but that isn't the question asked, is it?
But "better than nothing", which is what the original poster asked? Of course.