[GRASS-user] Importing ESRI .hdr Labelled raster via r.in.gdal
displays strange aliasing pattern
epatton at nrcan.gc.ca
Fri May 11 13:35:28 EDT 2007
I'm importing an Arc Floating-point raster using the 'EHdr/ESRI .hdr Labelled' driver in gdal:
$ gdalinfo 45_04_N_66_44_W_BATHY.flt
Driver: EHdr/ESRI .hdr Labelled
Size is 2641, 3721
Coordinate System is `'
Origin = (2481609.500000000000000,7340725.500000000000000)
Pixel Size = (1.000000000000000,-1.000000000000000)
Upper Left ( 2481609.500, 7340725.500)
Lower Left ( 2481609.500, 7337004.500)
Upper Right ( 2484250.500, 7340725.500)
Lower Right ( 2484250.500, 7337004.500)
Center ( 2482930.000, 7338865.000)
Band 1 Block=2641x1 Type=Byte, ColorInterp=Undefined
The projection is New Brunswick Double Stereographic (EPSG #2953). I have set up a Location with these projection parameters.
Th import seems to progress fine with no errors, but the imported raster doesn't display any data, just a jagged, greyscale grid. (A screenshot of the imported raster was too big to attach, but I can provide it in a separate email attachment if anyone is interested.)
I suspect, but am not sure, that I need to use gdal_translate instead and pass some CREATOPT parameters?
Also noteworthy is the fact that I had to do a tiny hack to the hdr file as per Frank Warmerdam's suggestion through the GDAL bugtracker:
(Background: I was received a malloc error when trying to import the ESRI Floating-point raster. See http://trac.osgeo.org/gdal/ticket/1573)
>From Frank Warmerdam:
"The problem is related to initialization when the NBITS keyword is missing
from the .hdr file. In 1.4.0 a bunch of new code was introduced for NBITS
< 8, but it also added a dependency on having the keyword present.
The workaround is to add "NBITS 8" in the .hdr file.
Fix is to default to 8 in the code. The fix has been committed in trunk,
and 1.4 branch and it should be released in 1.4.2."
I have added the above fix to the hdr file prior to using r.in.gdal to import the raster.
Any help appreciated!
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