Mike, While I would tend to agree that two identical GPS receivers nearby each other will tend to have a similar GPS altitude offset, this is not guaranteed to be true, due to the fact that each receiver may in fact see a different selection of satellites due to installation details and the different orientation of the aircraft etc.
Yes, calibration and instrument errors present their own problems for barometric altimeters. (Even errors due to static pressure variations in the cabin due to venting etc). I expect that using modern data fusion techniques could use both GPS altitude and pressure altitude for a highly reliable system. GPS altitude errors is also highly dependent on latitude. Near the equator is best, further away it can get quite bad. I routinely get reports of gps altitude errors in the UK of several hundred feet and my experience with a modern GPS engine is about 100 feet error. Over at www.flarm.ch there is a technical forum, perhaps we should direct these sorts of discussions over there. _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
