Formula for "NAV ON NAV" and "NAV SIGNAL"

Please can the SDK include the formulas that the sim used to calculate: (1)
NAV ON NAV (2) NAV SIGNAL NAV SIGNAL appears to be a function of Altitude &
Distance, with some limts placed on both Altitude & Distance. One assumes that
NAV ON NAV is then derived by a threshold value on the above calculated signal
? Are there any other items that affect these two values (currently in the
Simulation) ? ie Terrain ? Weather ? other preset variables ?

This is still a SDK documentation request…