Nah - that's DGPS with ground stations; they have their antennae at precisely surveyed points and then the system compares the received position from the satellites with the known position of the antenna and generates an XY and Z correction offset, which is transmitted encrypted (so you have to pay a subscription for the decode keyin order to usue it) and then received by the DGPS receiver (such as on a - ooooh - let's say a survey ship), which then applies the correction to it's own received GPS position. Typically we'll rock three receivers and receive corrections from three or four ground stations spread around a circle around our work area, with the three positions being fed into the nav software, which then'll mean out the three to one rather precise position.More to the point, how do members of the constellation calculate and correct their position? I seem to recall ground stations being used as a reference.
You don't actually triangulate using signals sent to and from the satellites, or "track" them. All the SVs do is transmit, at a lowly 50W, a time signal, an almanac and ephemeris data. In other words, all the SVs do is say, "At this time on this date I will be at this point in the sky and this high above the spheroid." The receiver does all the work, using trilateration, to determine your position from ranges and bearings; essentially a GPS satellite is a transmitter that sends out a big-ass look-up table of numbers - which is why you want a nice spread of seven to nine SVs around you to get a decently accurate fix.
It's a myth that "GPS can be used to track you." GPS receivers do just that - receive. The transmitter in your 'phone, however, can be used by software to broadcast your position once it has got it from the built in GPS receiver.
And here endeth the lesson.