Originally Posted by
Weston@HPTuners
The G-forces are measured using the phone's accelerometers. Usually when the reading is way off, it was due to the phone's position having been moved or rotated after the app auto-calibrated the accelerometer readings. It will do this prior to recording a session, the first time that it detects the vehicle stopped while the GPS signal appears good, and then possibly again right before you start recording if conditions permit. However, once recording has begin, it will definitely not do this, as to keep the readings consistent throughout the entire recording.