Similar methods, based on SRTM data ( grid 90x90, resp 30x30 m, or even finer data for some EU regions ) are used for the isolines in some OSM based maps, like the MapsForge compatible maps from OpenAndroMaps.
Some routers, like bicycle focused BRouter, use these data for elevation aware routing, as bikes are much more elevation sensitive then hikers or cars. Last, but not least, some outdoor GPS applications like LocusMap, optionally replace elevation data in the track log by SRTM elevation data, using bi-cubic grid interpolation. Due 2D position GPS fluctuation, there is also related SRTM altitude fluctuation on the sloped terrain. E.g. if there is slope 1 vertical m/ 5 horizontal m in the mountains, position fluctuations 10 m around the place lead to altitude fluctuations up to +/- 2 m of altitude. This is worse than barometric altitude, but better than GPS altitude. OTOH, these SRTM or the like data contain altitude artefacts due limited resolution. It is typical for cities ( "urban canyons"), wood/field borders, narrow valleys, rivers, bridges, tunnels. For such places, 2D position fluctuation can cause quite huge SRTM based altitude errors. For such and similar mountain-like cases, there is also an option to just use SRTM to correct the biggest GPS altitude errors. Dne 20/02/2018 v 18:45 Kevin Kenny napsal(a): > > I've also seen systems for surface navigation that take the geodetic > coordinates and obtain elevation from a digital elevation model. If > there's an accurate, high-resolution DEM available, that may be the > ideal compromise for drivers, hikers and such - they're seldom > anywhere but the surface, after all, and it avoids issues with > changing weather (for a barometer) and incompatibility of vertical > datums (for GPS). > > I love my wrist altimeter when hiking off-trail in mountains - it lets > me use any contour line as a backstop. I probably depend on it too > much, but the vegetation around here is usually too dense to allow for > sight resection - in fact, on off-trail trips, as often as not, a > viewpoint is the goal! -- Poutnik ( The Wanderer ) My Brouter profiles https://github.com/poutnikl/Brouter-profiles/wiki -- You received this message because you are subscribed to the Google Groups "Osmand" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
