Version 2 (modified by 17 years ago) ( diff ) | ,
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The gdal_translate
utility
The official documentation for the
gdal_translate
utility is http://www.gdal.org/gdal_translate.html.
When to use -a_ullr
Assign/override the georeferenced bounds of the output file.
Use the -a_ullr
option to add coordinates and pixel size to your raster. Using -a_srs
alone only adds information about coordinate system without modifying the coordinates themselves ( i.e. upper-left coordinates, pixel size and so on). So if the source image doesn't provide this information to gdal they need to be added by hand.
Syntax for PROJ.4 parameters
In trying to use the gdal_translate on a non-standard projection, the hardest part is often to determine what the allowable syntax and meaning of the PROJ.4 parameters were (i.e. +lat_0=70, +ellps=WGS84
) as an argument to -a_srs, -t_srs, -s_srs
. There is no clean ready made list, however the GeoTIFF projections transform list is a great start. Find the page for the projection you need and scan for the PROJ.4 Organization heading.
For example this Arcinfo projection:
Projection ALBERS Datum NAD83 Zunits NO Units METERS Spheroid GRS1980 Xshift 0.0000000000 Yshift 0.0000000000 Parameters 61 40 0.000 /* 1st standard parallel 68 0 0.000 /* 2nd standard parallel -132 30 0.000 /* central meridian 59 0 0.000 /* latitude of projection's origin 500000.00000 /* false easting (meters) 500000.00000 /* false northing (meters)
Becomes this in PROJ4 *:
+proj=aea +lat_1=61.66666666666666 +lat_2=68.0 +lat_0=59.0 +lon_0=-132.5 +x_0=500000 +y_0=500000 +ellps=GRS80 +datum=NAD83 +units=m
If it is a projection you use a lot, write it to a text file and refer to it like this:
gdal_translate ... -t_srs z:\common\yt-albers.proj4 ... infile.tif outfile.tif