"Arthur C. Clarke invented GPS."

I'm not an expert on the field of SF history, but my recollection is that Clarke proposed the idea of orbiting geostationary communications satellites, which to me is slightly different from inventing GPS.

Also, to the best of my recollection, Clarke did not patent the idea, and never made a dime of revenue off of it; Doctorow, as I read that Twitter comment, is citing this as a revenue stream for Clarke.