[Gdal-dev] Converting .bmp to GeoTIFF

[Frank Warmerdam]

Don Tidrow wrote:
> Can any of the gdal utilities be used to add georeferencing data 
> (corners in UTM) to a .bmp file and output the result to a GeoTIFF file? 
>  If so, how?  Eventually I'll want to reproject the resulting GeoTIFF to 
> lat/long, which I think gdalwarp can do, but I haven't figured out if 
> gdal_translate can do this conversion.

Don,

The -a_srs option in gdal_translate can be used to assign a coordinate
system to a file as it is copied.  However, setting the corner coordinates
is not so simple.  One approach would be to write an ESRI style world file
for the .bmp.  World files generally look like this:


            60.0000000000
             0.0000000000
             0.0000000000
           -60.0000000000
        440750.0000000000
       3751290.0000000000

The values are <x pixelsize>, 0, 0, <negative y pixel size>, <topleft X>,
<top left y>.

So, given a bmp file called abc.bmp you would write an abc.wld file with
the top left corner and pixel size, and then you could use a command like
this to turn it into a UTM GeoTIFF file:

gdal_translate abc.bmp abc.tif -a_srs '+proj=utm +zone=11 +datum=WGS84'

The gdalwarp program also has something similar to the -a_srs flag but
it is -s_srs.  So to warp directly to lat/long you would still write the
.wld file, and use a gdalwarp command like:

gdalwarp -s_srs '+proj=utm +zone=11 +datum=WGS84' \
    -t_srs '+proj=latlong +datum=WGS84' abc.bmp abc.tif

Best regards,

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