[ansgri]

They probably use some RTK / dGPS setup for increased accuracy, which does need calibration.

[PragmaticPulp]

Actual RTK/dGPS makes GPS more accurate, not less. If it doesn’t lock, the software should fall back to regular GPS.

Unless they were abusing the system by putting the dGPS reference station on a moving vehicle going the opposite direction or simply feeding spoofed correction data into the GPS.

[neeleshs]

I'm ignorant about speed tests. Given that distance is constant, wouldn't two synchronized timers be simpler than using GPS? And potentially more accurate?

[olyjohn]

I think timing it between two points will give you average speed between them. But this record is about top speed.

[neeleshs]

Ah! thanks!