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Hi Bas,<br>
<br>
Thanks for that. I am indeed attempting to project back to the same
projection as MSG images (I've been messing about with the dimensions,
but it was originally 3712, like you say). We're trying to mix imagery
before any further reprojection, but I don't think it's going to be
possible - at least not with GDAL.<br>
<br>
It seems that gdalwarp doesn't calculate the extreme pixel extents
before commencing the reprojection. I know this can't be wholly true
because it does an excellent job with other projections (e.g. ortho).<br>
<br>
Many thanks for spotting the incorrect height. Not sure how we arrived
at the original figure. So at least we now have a view which is 95% in
keeping with the MSG product. I'll struggle on for a little longer
with GDAL, and then give ILWIS a go ;-)<br>
<br>
Andy<br>
<hr size="2" width="100%"><br>
<br>
Bas Retsios wrote:
<blockquote cite="mid:479F275E.7070800@itc.nl" type="cite">Hi!
<br>
<br>
We use the geos projection in gdalwarp, but only as a source (not as a
target).
<br>
The images we receive in geos projection are from the meteorological
satellites Meteosat-8 and Meteosat-9 (MSG).
<br>
And the size of most bands is 3712x3712 pixels.
<br>
<br>
I noticed your 3700x3700 images, therefore I got curious: are you
trying to convert back to the projection of the MSG images?
<br>
<br>
Anyway, the only suspicious part I noticed in your gdalwarp command is
the +h=745331460 parameter.
<br>
+h is the satellite height, in meters. This "height" is the distance
from the ellipsoid (thus not from the centre of the earth). For MSG
(which is a geostationary satellite), the correct value is +h=35785831.
<br>
Your value is about 20 times higher, which is two times the earth-moon
distance. Are you sure you have an image taken from that far away?
<br>
See also:
<br>
<a class="moz-txt-link-freetext" href="http://www.remotesensing.org/geotiff/proj_list/geos.html">http://www.remotesensing.org/geotiff/proj_list/geos.html</a>
<br>
<br>
Cheers,
<br>
<br>
Bas.
<br>
<br>
</blockquote>
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