----- gerard robin a écrit : > > SRTM is about ground elevation. Coastline is a > > different topic and experience has shown that all these nice attempts > > to automagically derive coastlines from imagery, be it SWBD or PGS, > > return pretty flaky results. Unfortunately .... > > Well, i thought that costline was calculated with the intersection > of the sea level (or water level) and the ground altitude. > I was wrong, my imagination was (is) out of reality. :)
It is not impossible. In srtm4, sea level is not 0 but a special value, so I guess the CGIAR ( the body releasing this improved dataset ) processed the data in order to detect sea. But this is raster data, not vector, and it has the 3-arc second resolution. There are teams that are also trying the derive flow direction and rivers from the srtm dataset. Blue Marble NG has bathymetry data too, so in theory, the algorithm I use could model the ground floor and add water level procedurally. There are special case like Death Valley or the Dead Sea that have dry land under the mean sea level, and lakes level are often higher than sea level. -Fred -- Frédéric Bouvier http://my.fotolia.com/frfoto/ Photo gallery - album photo http://fgsd.sourceforge.net/ FlightGear Scenery Designer ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
