[gdal-dev] Wrong sliding when AREA_OR_POINT metadata is edited?

[Rahkonen Jukka (MML)]

Hi,

See this and find test data and example commands https://github.com/opengeospatial/OGC-API-Sprint-August-2020/issues/18.

If PixelIsPoint image has these GeoTIFF tags

Geotiff_Information:
   Version: 1
   Key_Revision: 1.0
   Tagged_Information:
      ModelTiepointTag (8,3):
         0                 0                 0
         -90               90                0
         1024              0                 0
         0                 90                0
         0                 1024              0
         -90               0                 0
         1024              1024              0
         0                 0                 0
      End_Of_Tags.
   Keyed_Information:
      GTModelTypeGeoKey (Short,1): ModelTypeGeographic
      GTRasterTypeGeoKey (Short,1): RasterPixelIsPoint

and PixelIsArea has the same tags except GTRasterTypeGeoKey (Short,1): RasterPixelIsArea

Now shouldn't the PixelIsPoint image slide half a pixel to the left and upwards compared to PixelIsArea image? If I run these images through gdalwarp the warped pixel_is_area image shows corner coordinates Upper Left  (-180.0000000,  90.0000000) and pixel_is_point image Upper Left  (-179.9560547,  89.9560547), so sliding happens to the right and downwards.

It is late and I feel fuzzy but shouldn't the pixel_is_point variant has smaller easting, greater northing instead, thus (-180,0439453, 90,04394531)?

The images are georeferenced with tiepoints/GCPs, perhaps it adds something to the soup?

-Jukka Rahkonen-




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