[gdal-dev] Apply Vertical Grid Shift to coordinate

[Matthias Kuhn]

Thanks a lot for the help, Even.

That just saved me some headache.

I'll respectfully approach the source of this data before trying to figure
out where to put tabs and line breaks and warping.
And then crossing fingers that the national administration open sources the
data in a usable format rather sooner than later to prevent people from
jumping through hoops.

Best wishes !
Matthias

On Thu, Oct 22, 2020 at 10:17 PM Even Rouault <even.rouault at spatialys.com>
wrote:

> >
> > $ head geoid+HTRANS_ETRS2020.gtx
> > 45.75 5.85  0.00833333333333333333 0.00833333333333333333 253 559
> > 49.4610
> > 49.4649
> > 49.4720
> > 49.4823
> > 49.5021
> > 49.5511
> > 49.5899
> > 49.5819
> > 49.5588
> >
>
> This is definitely not a GTX file. GTX is a binary format. I don't think
> there's an existing GDAL driver for the above variant.
>
> You'll have to write your own convertion script or modify the file to look
> like something recognized by GDAL, like a AAIGRID file. Or yell at the
> person
> who provided that file to you to not use something known by GDAL.
>
> The header line is likely:
> south_latitude (I guess for Switzerland)
> west_longitude
> vertical_resolution (or horizontal_resolution ?)
> horizontal_resolution (or vertical_resolution ?)
> height_in_pixels (or width_in_pixels ?)
> width_in_pixels (or height_in_pixels ?)
>
> If you map that to headers of AAIGRID, that could work. That looks like:
> ncols        20
> nrows        20
> xllcorner    440720.000000000000
> yllcorner    3750120.000000000000
> cellsize     60.000000000000
>
> You'll perhaps have to do a vertical flip depending on the convention of
> your
> file (can be done for example by switching top and bottom Y with
> gdal_translate -a_ullr and then gdalwarp)
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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