[Proj] Dutch correction grid

[Jan Hartmann]

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 ...

Jan

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.
>
> Regards
>
> 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
>     GDAL
>     > 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
>     arcseconds.
>     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?
>
>     Jan
>
>     Driver: GTiff/GeoTIFF
>     Files: dxy.tif
>     Size is 400, 400
>     Coordinate System is:
>     GEOGCS["RT38",
>         DATUM["Stockholm_1938",
>             SPHEROID["Bessel 1841",6377397.155,299.1528128000008,
>                 AUTHORITY["EPSG","7004"]],
>             AUTHORITY["EPSG","6308"]],
>         PRIMEM["Greenwich",0],
>         UNIT["degree",0.0174532925199433],
>         AUTHORITY["EPSG","4308"]]
>     Origin = (3.386235000000000,50.762069400000001)
>     Pixel Size = (0.009627452750000,0.007066402750000)
>     Metadata:
>       AREA_OR_POINT=Area
>     Image Structure Metadata:
>       INTERLEAVE=PIXEL
>     Corner Coordinates:
>     Upper Left  (   3.3862350,  50.7620694) (  3d23'10.45"E,
>     50d45'43.45"N)
>     Lower Left  (   3.3862350,  53.5886305) (  3d23'10.45"E,
>     53d35'19.07"N)
>     Upper Right (   7.2372161,  50.7620694) (  7d14'13.98"E,
>     50d45'43.45"N)
>     Lower Right (   7.2372161,  53.5886305) (  7d14'13.98"E,
>     53d35'19.07"N)
>     Center      (   5.3117256,  52.1753499) (  5d18'42.21"E,
>     52d10'31.26"N)
>     Band 1 Block=400x1 Type=Float64, ColorInterp=Gray
>     Band 2 Block=400x1 Type=Float64, ColorInterp=Undefined
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