Anyone noticed that the EXIF data in still images has an altitude stamp? However the value doesn't match the altitude displayed in the app. It might be an uncalibrated altitude straight from the mini's barometric sensor as it seem to be vaguely similar to altitude above sea-level. It won't know the current atmospheric pressure so perhaps it has a nominal value for this. When you take off the app will be able to get a barometric reading to use for 0m altitude for that flight.