Little simple math here..................

Speed 1mph =14.6 feet per second
speed .65mph= 9.5 feet per second

Accuracy of HB gps 3 meters this near 9 feet

If you move more than 9 feet per second (.65mph), the gps shows you moving and no donut.

Pings from heaven come every second, so the gps receives signals and calculates to see if you moved out of the 9 foot area. This happens every second.

GPS says: Did I move, if so, how far from last position (9 foot). Over and over and over.

Of course it is more complicated than this, but this is the rough basics of the math.

I kinda simplified it somewhat.