Norman Vine writes: > David Megginson writes: > > > > Norman Vine writes: > > > > > Have you tried preinserting some of the the higher res srtm1 data > > > to terra innide of and on the edges of the airport polygons ? > > > > > > This shoud be quite accurate. > > > > Maybe *too* accurate -- at the resolution, a 747 parked on the field > > will start to show up in the elevations, not to mention large hangars > > and the terminal buildings. > > Whatever, the point is try preinserting some points for the airports > I think you will be pleasantly surprised :-)
I would worry that preinserting points would yield spikes whenever the FAA surveyed elevation differs from the SRTM data ... in otherwords imagine the SRTM surface with spikes whereever we place our "pre-inserted" points. I think we would have to use the FAA surveyed data as "error" correction terms and then interpolate these error correction terms over the surface. I plan to try that sometime when I get some time. In otherwords ... start with the list of FAA surveyed points that you know for certain. For each of these also calculate the corresponding SRTM elevation. Now subtract the two to get the difference (or error term.) Do this for all the FAA surveyed points. Now build a list of points of the form: (lat, lon, error) and triangulate that. Now for each point of the airport you can compute a true elevation by taking SRTM height + the error term interpolated from our error surface. Not sure if that would introduce more problems than it solves but it gives me warm fuzzy feelings at the moment. :-) Curt. -- Curtis Olson HumanFIRST Program FlightGear Project Twin Cities curt 'at' me.umn.edu curt 'at' flightgear.org Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
