[Magnum44]

It would be impossible to have regional GPS outages if the GPS system were satellite based. This is evidence that GPS is ground based.

Uh...no. The interference sources are ground based. All one has to do is create enough noise in the GPS frequency band that the GPS satellite based signals are masked. It does take a considerable amount of noise since GPS signals and receivers are designed to be distinguishable with noise, but at some point the receiver can no longer track the signal.

[TruthInThoughtWordAndDeed]

Then please explain the bit about the signal disappearing as you drive south into Mexico.