This interest stems from my long-time interest in orbits, computations, and applied mathematics in general. I started out as a math/physics major and never lost my interests beyond electrical engineering.
I am professionally active with the design GPS projects so will not comment further on that, but to say that this is an intriguing interest of mine as well. The GPS module here is also used to frequency lock a precision OCXO to the PPS signal for use as the precision reference in the AM1-S100 frequency source.
This work also ties in directly with the photogrammetry-based project that I already have underway.