[jcrawfordor]

It is very hard for me to understand what they're referring to with discussion of calibration. They would presumably be using some type of augmented GPS/differential GPS which could require calibrated ground stations depending on accuracy targets, but the error you'd get from using unaugmented GPS or a low-setup augmented GPS like WAAS wouldn't be large enough to account for the errors discussed here. A cheap consumer GPS receiver like the one in your phone shouldn't produce the errors in question over a meaningful distance outside of some really fringe situations.

One of the specific claims is that the GPS equipment doesn't show a speed of zero when the vehicle is not moving - it's hard to understand how this would happen, a poorly set up DGPS scheme would not produce a 20mph rate of change in fixes for a non-moving object unless it was seriously defective.

All in all it feels a lot like the "calibration" here is just a hand-waving excuse for the outcome - the margin here is so large that calibration issues are not going to account for it unless there was outright incompetence.

The vendor involved, DEWE, makes various types of augmented GPS equipment but also inertial measurement products. Calibration would be a much bigger issue with inertial measurement and that could make more sense, but all the reporting on this says GPS was in use.