So I cant bounce a signal off the atmoplane and send it back to you making it look like a degree off the horizon?
You wouldn't be able to bounce signals off of the atmosphere and get angles above a certain limit. Although the highest value on that diagram is 68°, there are frequently angles greater than that. Bouncing signals in the atmosphere has fairly shallow angle limits, this is why there is a "dead band" for MF and HF radio communications after you get out of direct path signals, but where the angles don't allow the reflection of the radio signal.
The supposed "degrees" off the horizon could just be built into the program because that is where the sat is "supposed" to be. While actually still receiving a a signal from a land based tower.
The program has to take into account the motion of the rig. We have motion reference units (MRU) that feed a signal to the demodulator to correct for this. There is no mechanism that will allow for a land based signal to give these results.
Either one of those scenarios is plausible.
Not with the current models of radio communication.