Martin Spott wrote:

Does this mean to get the best out of the available sources you need
SRTM data for the elevation and land cover, VMAP0 for inland water
(lakes and rivers) and GSHHS for the ocean shoreline ? Anything else ?
Merging these sources sounds like a 'funny' game ....

Funny in the sarcastic way. This is actually an extremely difficult problem, because vmap0 and GSHHS have some overlap, and eventually, they have to join up: for example, at a certain point the Hudson River stops being part of the ocean shoreline and starts being inland water--it would be a very bad thing if the river stopped, jumped 500m to the east, then started again.

vmap0 is not internally consistent anyway, but things get even worse when you try to combine vmap0 roads and railroads with GSHHS coastlines: you'll find roads that are supposed to hug the coast jumping out into the middle of a lake or ocean even more often.

What we really need to do, as Norm has often suggested, is load all of this data into a single GIS with a nice graphical interface and start working on reconciling it: for example, we can pick the best coastline between GSHHS, vmap0, and vmap1 (where available), use the higher-resolution US road data combined with the lower-resolution vmap0 road data for the rest of the world, tweak roads to go around airports and follow coastlines, etc. etc. That's obviously a big job, and it probably shouldn't be limited to FlightGear. I think that there are already the equivalent of open source GIS projects working on this kind of thing, but I don't know how far they've come in practical terms.

All the best,


Flightgear-devel mailing list

Reply via email to