General Relativity fully describes Special Relativity plus some. You can start with General Relativity, make some assumptions (gravity is small, objects are bigger than a flea, …) so that some terms are negligible and you end up with Special Relativity. If you use General then you’ll always get a more accurate answer but the math is harder.
General Relativity fully describes Special Relativity plus some.
Jake Flickinger
1

Here’ s why it seemed that the General somehow excludes the Special:

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

Special Relativity predicts.. atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day”

“ A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day.”

“The combination of these two relativistic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)”

Any explanation of that? Thanks.