Ralf Gerlich wrote:
Hi,
David Megginson schrieb:
The problem, though, is not the accuracy of the shorelines (though
that's obviously important), but the type -- for some reason,
TerraGear has started to misinterpret the Great Lakes as ocean rather
than lake, and thus, it's cutting them right out of the scenery rather
than using the SRTM elevations.
It seems that it's exactly that. I wasn't yet able to verify that, but
it seems that the Great Lakes are not part of the landmass and are
thus zeroed in altitude. I'm not sure why that worked in the previous
releases.
Hmmm, if the great lakes are not included as part of the world land
mass, then they would indeed get interpreted as ocean by terragear and
flattened to zero elevation.
I suspect that in the GSHHS data, the great lakes are included in the
land mass and in the VMAP0 data the great lakes are not part of the land
mass.
In previous scenery builds we used GSHHS ocean/land mass data for the
basic outline of the world (but discarded all GSHHS lake/river data.)
We used VMAP0 for all internal lakes and rivers since arguably those
were 'more accurate'.
However, GSHHS and VMAP0 don't always agree on what areas of water are
lake versus ocean, so there are places that come out dry because GSHHS
calls it a lake (so we ignore it from that data set) and VMAP0 calls it
an ocean so we ignore it from the vmap0 data set.
For this latest scenery build I used VMAP0 only and didn't uses any
GSHHS data. This led to many reported improvements in many areas where
the above mentioned conflict was automatically resolved. But vmap0 is
not very accurate so we have a lot of buildings and objects now in the
water, and we have the great lakes at zero elevation.
Martin: please explain again in very great detail for me how exactly
GSHHS has been improved?
Thanks,
Curt.
--
Curtis Olson http://www.flightgear.org/~curt
HumanFIRST Program http://www.humanfirst.umn.edu/
FlightGear Project http://www.flightgear.org
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