[Gdal-dev] projection with GEOS

[Hannes Isaak Reuter]

Hallo Gdals,

After experimenting around now the second day and not reaching close 
to a solution, here the question..

I have a hdf file which is supposed to be in the GEOS projection, 
which I would like to have in WGS84

So, what I do is creating a tif with GCPS

gdal_translate -gcp 1 29 -45,06 76,49 -gcp 1 229 -15,29 53,95 -gcp 1 
429 -12,08 43,56 -gcp 1 651 -10,44 34,60 -gcp 101 15 -33,11 78,23 
-gcp 101 229 -10,17 53,75 -gcp 101 429 -8,08 43,46 -gcp 101 651 -7,00 
34,54 -gcp 201 7 -17,42 78,94 -gcp 201 229 -5,21 53,63 -gcp 201 429 
-4,16 43,40 -gcp 201 651 -3,61 34,50 -gcp 301 3 -1,34 80,71 -gcp 301 
229 -0,4 53,59 -gcp 301 429 -0,7 43,37 -gcp 301 651 -0,4 34,49 -gcp 
401 6 15,60 79,29 -gcp 401 229 4,53 53,62 -gcp 401 429 3,61 43,39 
-gcp 401 651 3,14 34,50 -gcp 501 14 29,69 77,92 -gcp 501 229 6,47 
53,73 -gcp 501 429 7,53 43,45 -gcp 501 651 6,53 34,53 -gcp 601 27 
42,16 76,42 -gcp 601 229 14,56 53,92 -gcp 601 429 11,52 43,54 -gcp 
601 651 9,96 34,59 -gcp 701 46 50,92 74,18 -gcp 701 229 19,92 54,20 
-gcp 701 429 15,61 43,68 -gcp 701 651 13,45 34,67 -gcp 801 71 57,03 
71,55 -gcp 801 229 25,69 54,59 -gcp 801 429 19,86 43,87 -gcp 801 651 
17,04 34,79 -gcp 901 102 62,17 68,82 -gcp 901 229 32,13 55,12 -gcp 
901 429 24,34 44,11 -gcp 901 651 20,75 34,93 -gcp 1001 140 64,66 
65,61 -gcp 1001 329 32,86 49,54 -gcp 1001 529 26,68 39,97 -gcp 1001 
651 24,62 35,10 -gcp 1101 185 66,80 62,33 -gcp 1101 329 39,32 50,12 
-gcp 1101 651 28,72 35,32 -gcp 1201 237 69,52 59,09 -gcp 1201 329 
47,24 50,93 -gcp 1201 651 33,10 35,58 -gcp 1301 297 72,54 55,79 -gcp 
1301 329 58,94 52,27 -gcp 1301 651 37,91 35,90 -gcp 1401 367 74,10 
52,10 -gcp 1401 651 43,31 36,29 -gcp 1501 448 75,27 48,16 -gcp 1501 
651 49,71 36,81 -gcp 1601 542 76,37 43,94 -gcp 1601 651 58,07 37,54 
-gcp 1700 651 77,40 39,39 HDF5:"HDF5_FVC200612020000.hdf"://FVC testdd.tif

this seems to work..

Next step would be to reporject that tif to WGS84 with the following line

gdalwarp -s_srs "+proj=geos  +lon_0=10 +h=35785831m +x_0=0 +y_0=0" 
-t_srs WGS84 testdd.tif test270106.tif

However this delivers a tif which is completly out of the data range 
( from 9 to 10 degress in x extent)

If I apply

gdalwarp -s_srs WGS84  -t_srs WGS84 testdd.tif testutm.tif

at least the image comes closer to the desired location, still up to 
2 degress off.. so no real solution ..


Last think i tried was to warp the image without GCPs to WGS84, still 
thats not working .. see below..
gdalwarp -s_srs "+proj=GEOS  +lon_0=10 +h=35785831km +x_0=0 +y_0=0" 
-t_srs WGS84 testdd5.tif testdd6.tif
ERROR 1: Unable to compute a transformation between pixel/line
and georeferenced coordinates for testdd5.tif.
There is no affine transformation and no GCPs.



Can anyone shed a little bit more light on how to reproject GEOS 
imagery using GDAL ?


Hannes