Robert Vollmert wrote: > Not sure how common they are, but there's some GPS units with built-in > barometer (Garmin Etrex Vista HCX at least). The data they provide > should be good enough to be useful. > Those sensors need calibration against a known point and can give a huge offset when uncalibrated. I have such a GPS (GPSmap 60CSx) and never calibrate it as will most others presumably. As a cyclist all I'm interested in is the relative altitude differences not the precise actual altitude as opposed to, say, skydivers. Measuring relative altitudes is quite accurate (+/- few meters) though. The data is useless when you want to use it as a primary source, but it should be alright if you want to use it to determine offsets when compared with a known point. This requires you to process the GPX nodes trace-by-trace so you can determine the offset from which the trace started.
I appose to using altitude data on nodes. E.g. one would not be able to move a node when that data is added without having to correct/remove the height data as well. Also adding altitude data invites to add -otherwise useless- nodes everywhere. I prefer to have altitude data kept apart from OSM database. Perhaps our own SRTM database corrected/enhanced using our traces. _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
