[Qgis-user] Geolocating .flt files

[Even Rouault]

On jeudi 9 mai 2019 19:31:55 CEST Quinn, Gary wrote:
> I am new to Qgis.
> 
> I have an .flt (floating point raster) file and an associated .hdr file.
> I can import the .flt  image file into Qgis (using Add raster layer), and
> the image displays correctly.
> But how do I geolocate this image using the associated .hdr file?
> In other words, how do I make Qgis use the .hdr file to let me know the
> lat/lon of each pixel on the display?
> 
> Note: The .hdr file is like this:
> geo points  = {     1,     1,  -40.212464,  146.355212,     1,  2590,
> -44.006326,  145.100364,  1024,  2590,  -44.252673,  146.901021,  1024,
>  1,  -40.442148,  148.049722}
> 
> So I want Qgis to use this .hdr information to geolocate the image.
> I have searched various info about using .flt images and geolocation but
> can't find anything.

Gary,

Those are ground control points in the ENVI format:
https://www.harrisgeospatial.com/docs/ENVIHeaderFiles.html

GDAL can write those, but not read them, hence the georeferencing is ignored. 
I've filed https://github.com/OSGeo/gdal/issues/1528 about that

In the meantime you could use the georeferencer to add manually the ground 
control points.

As documented, the values in geo points are a succession of
pixel_x_coordinate, pixel_y_coordinate, latitude, longitude
Note: you must substract 1 to pixel_x_coordinate and pixel_y_coordinate since 
the GDAL/QGIS convention for origin of a raster is (0,0) whereas ENVI uses 
(1,)

Even

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