[Proj] Dutch correction grid
j.l.h.hartmann at uva.nl
Tue May 3 04:30:18 EST 2011
Ah, my usual fault: I still used gdal 1.7, where there is no NTV2
format. I compiled 1.8 and now it is available. Getting closer ...
On 04/29/11 23:39, Jose Gonçalves wrote:
> The +nadgrid command expects a NTv2 file, with extension gsb, not a
> tiff file. You must use gdal_translate to convert it to the NTv2
> format. I think that's what Frank Warmerdam referred in a previous email.
> Jose' A. Gonçalves
> 2011/4/29 Jan Hartmann <j.l.h.hartmann at uva.nl
> <mailto:j.l.h.hartmann at uva.nl>>
> (About creating a grid shift file for the Dutch RD projection):
> On 04/08/11 18:29, Frank Warmerdam wrote:
> > As input we would require an input raster with two "bands"
> > representing the
> > offset in longitude and latitude. I'm not sure off hand what
> the units
> > are - possibly arcseconds? The input file would need to be
> > georeferenced
> > in latitude and longitude.
> > If your input points are sparse and irregular you could likely use
> > gdal_grid to interpolate a grid from the point data.
> > My point was mainly that you don't necessarily have to write an NTv2
> > "writer" - it is sufficient to get the datum shift data into any
> > support grid format.
> > Best regards,
> I made a 400*400 gdal raster called dxy.tif with two bands, the first
> with offsets for longitude, the second for latitude, all in
> If I use this file in the +nadgrids clause of cs2cs, I don't see any
> difference in the output. If I change the filename into something
> non-existing, I don 't see any differences either and do not get an
> error message. Any idea how I can test this further?
> Driver: GTiff/GeoTIFF
> Files: dxy.tif
> Size is 400, 400
> Coordinate System is:
> SPHEROID["Bessel 1841",6377397.155,299.1528128000008,
> Origin = (3.386235000000000,50.762069400000001)
> Pixel Size = (0.009627452750000,0.007066402750000)
> Image Structure Metadata:
> Corner Coordinates:
> Upper Left ( 3.3862350, 50.7620694) ( 3d23'10.45"E,
> Lower Left ( 3.3862350, 53.5886305) ( 3d23'10.45"E,
> Upper Right ( 7.2372161, 50.7620694) ( 7d14'13.98"E,
> Lower Right ( 7.2372161, 53.5886305) ( 7d14'13.98"E,
> Center ( 5.3117256, 52.1753499) ( 5d18'42.21"E,
> Band 1 Block=400x1 Type=Float64, ColorInterp=Gray
> Band 2 Block=400x1 Type=Float64, ColorInterp=Undefined
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