Hi there,
The rasters we tried to import into Koordinates have slightly incorrect extents specified in the GeoTIFF tags, e.g. upper left corners of (-180.0083333, 90.0083333), which translates into half a pixel offset. Are the GeoTIFF extents calculated from pixel centers rather than edges?
The TFW world files are fine, but we prioritise use of GeoTIFF tags.
Thanks for the great work.
@ EdCorkery: I’ll let Tom follow up about this. My guess is yes, these are measured from the center of the pixel rather than the top left. If that is true, the extent should start at an upper left more like: -179.9916666, 89.9916666 (1/2 of 1 km grid cell size) rather than outside the 180°, 90° bounding box.
Ed, We’ve heard back from the software developer who’s now investigating. I’m seeing the same error as you in ArcGIS.
Hello. I am the author of Natural Scene Designer Pro, which will georeference a raster image.
When it saves a GeoTIFF it uses the same values in the GeoTIFF tags as it does in the TFW file. As a test, I georeferenced a world raster dataset and verified that the upper left corner in both the TFW file and the GeoTIFF tag is (-180, 90), not (-180.0083333, 90.0083333)
One of the GeoTIFF tags (GTRasterTypeGeoKey) dictates whether the reference
coordinate is the upper left (RasterPixelIsArea) or center (RasterPixelIsPoint) of the pixel.
NSD Pro always sets the raster type as ‘RasterPixelIsArea’. This means that the upper left corner of the upper left pixel is (-180,90).
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