Gerard, gerard robin wrote:
> 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. :) No you're correct. The point is: Automagically calculating the intersection of terrain with sea level is unreliable because a) the elevation data is too inaccurate and b) tides make a huge difference - which also adds to a). My favourite place to demo is here - and, actually, comparing coastlines was one of the most prominent motivations to start this MapServer project several years ago (attention, long URL): http://mapserver.flightgear.org/ms?img.x=363&img.y=307&layer=v0_landmass&layer=gshhs_coastline&layer=pgs&layer=swbd&zoomdir=0&zoomsize=2&imgxy=300.0+300.0&imgext=6.750212+53.529021+7.000212+53.779021&root=&savequery=true&program=%2Fms The red one of these four coastlines, GSHHS, is sometimes a bit coarse (when you have a _very_ detailed look at it) but it's still the most accurate - it has seen manual review. The green one (VMap0) is the one we're currently using. The two automagically derived coastlines (PGS and SWBD) are both far off .... You'll see similar results at New Orleans and many, many other places in the world, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -------------------------------------------------------------------------- ------------------------------------------------------------------------- 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
