Sort of. I know a little about this from working in the oilfield. If you think navigating in the sky is tricky, try navigating underground. We had the BGGM[1],

Sort of. I know a little about this from working in the oilfield. If you think navigating in the sky is tricky, try navigating underground. We had the BGGM[1], a model of the Earth's magnetic field, that gives us magnetic field strength and direction, given lat/long, altitude, and date. Accuracy was around 0.5deg in direction and I think 0.5% in strength. I'm not sure about the validity of it at more exotic locations and high altitudes, though. We used it as an accuracy check when taking field measurements to determine direction. I can elaborate if anybody's interested. As for using the data to check aircraft location, if the model is reasonable valid in those conditions, it might work as a sanity check. I doubt it would be practical to reverse it and get location from field information, though. It's already tough to get really good field data in an environment filled with metal objects and electric currents, though. [1] http://www.geomag.bgs.ac.uk/data_service/directionaldrilling/bggm.html http://www.geomag.bgs.ac.uk/data_service/directionaldrilling...