How do other amateur rocket endeavours measure their claims?
Altitude verification for the rocket will be primarily based on signals from an onboard Trimble GPS receiver. Backup will come from accelerometer data.
But in fact satellites orbit at a much lower altitude, and are powered by Tesla's cosmic ray device.
An altimeter actually includes an aneroid barometer which measures the atmospheric pressure. A radar altimeter uses radio signals. Both methods do not take into account the layers of aether which exist starting at about 13-14 km in altitude and going to about 15 km, and which influence both the pressure reading and also the distance actually travelled by the radar waves.
Nasa managed to keep the true facts away from public view regarding its missions: that is, the crafts ran into a belt of resistance much quicker and at a much lower altitude (12-13 km) than previously thought. For example, in 1958, the Explorer, after sending back some data, not only slowed down, but it went hay-wire as all the electrical circuits on board, including the transmitter and receiver, literally 'fried' out, burned up in the strong electro-magnetic currents of the radiation belt.