Steve Bennett wrote: > Garmin Oregon 550.
I see that's got a barometric altimeter too. Very good. > Ah. What is "GPS-derived altitude" though, exactly - does it rely on a > model of the earth's surface, or is it effectively computing the > distance from the satellites? Purely from satellites, definitely. Others on the list are likely much more up to speed with the technicalities. > Anyway, my recorded elevation for Mt Ossa is 1613m, and the Acropolis > is 1477m. Wikipedia gives Mt Ossa as 1614, and the Acropolis as 1481m. > Maybe this method is more accurate than I was expecting... > > OTOH, I'm still not convinced that all this is necessary. Surely using > figures from an authoritative source would serve everyone a lot > better... Yes, the figure from a proper survey should have an accuracy of a few centimetres. One of my many jobs (back in the 70s) was a chainman (surveyor's assistant). With modern electronic gear, I believe there's no such job any more. John H _______________________________________________ Talk-au mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-au
