[Geotiff] Polar Stereographic GeoTIFFs

[Merold]

Hi!

I am trying to store some image data using Polar Stereographic projection
into GeoTIFF format. I first tried some data using Polar Stereographic North
projection, which seemed to work.

But then I tried the Polar Stereographic South projection and the results
are wrong.

I am not sure whether the GeoTIFF really supports the projection I am using,
since the projection plane of my map is not tangetial to the earth poles
only, but intersects the earth at a specific latitude.

For the northern example I use as downward longitude 10 degrees east and the
projection plane is at 60 degrees north.

For the southern test, I used as downward longitude 160 degrees west and for
the projection plane 60 degrees south. I checked the resulting GeoTIFF using
ENVI Freelook. The latitude values seem to be almost correct, but the
longitude seems to be rotated by 180 degrees.

I then tried another sample using Polar Stereographic south with the
downward longitude at 180 degrees east and the projection plane at 0 degrees
south. This time the longitude values are correct, but the latitude has the
inverted sign (so the results have the correct value in degree, but are
given for the northern hemisphere).

Then finally I tried to define basically the same image but using as
downward longitude 180 degrees WEST and projection plane at 0 degrees south.
That should be the same georeference information basically.
But this time the resulting coordinates given in ENVI Freelook are constant
over the entire image.

Could anybody help me with this problem?

I have placed the GeoTIFF sample images on my webspace. They can be found
under:

http://freenet-homepage.de/merold/MSG2_1_TEST.tif
(Polar Stereographic North, first sample, seems okay)

http://freenet-homepage.de/merold/MSG2_2_TEST.tif
(Polar Stereographic South, first sample, latitude okay, but longitude
wrong)

http://freenet-homepage.de/merold/MSG2_3_TEST.tif
(Polar Stereographic South, second sample, longitude okay, but latitude
wrong sign)

http://freenet-homepage.de/merold/MSG2_4_TEST.tif
(Polar Stereographic South, third sample, completely wrong)


Thanks,
Carsten

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