[gdal-dev] Apply Vertical Grid Shift to coordinate

[Even Rouault]

> 
> $ 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

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