Changes

The method entails observing a fast moving Global Navigation Satellite Systems (GNSS) satellite has a have very accurately known sky-coordinate for a given time. By comparing the observed sky-coordinate of the satellite in your images (after doing astrometric calibration of your images) to the predicted sky-coordinate of the satellite at the respective header time (and knowing the sky-rate of the satellite) it is possible to determine the accuracy of the time-stamps in your images image headers.