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GDAL Utilities

The following utility programs are distributed with GDAL.

gdalinfo

The gdalinfo program lists various information about a GDAL supported raster dataset.

Usage: gdalinfo [-mm] datasetname

The -mm switch will force computation of the actual min/max values for each band in the dataset.

The gdalinfo will report all of the following (if known):

• The format driver used to access the file.
• Raster size (in pixel and lines).
• The coordinate system for the file (in OGC WKT).
• The geotransform associated with the file (rotational coefficients are currently not reported).
• Corner coordinates in georeferenced, and if possible lat/long based on the full geotransform (but not GCPs).
• Ground control points.
• File wide (including subdatasets) metadata.
• Band data types.
• Band color interpretations.
• Band block size.
• Band descriptions.
• Band min/max values (internally known and possibly computed).
• Band NODATA value.
• Band overview resolutions available.
• Band unit type (ie. "meters" or "feet" for elevation bands).
• Band pseudo-color tables.

Example:

warmerda@gdal[138]% gdalinfo ~/openev/utm.tif 
Driver: GTiff/GeoTIFF
Size is 512, 512
Coordinate System is:
PROJCS["NAD27 / UTM zone 11N",
    GEOGCS["NAD27",
        DATUM["North_American_Datum_1927",
            SPHEROID["Clarke 1866",6378206.4,294.978698213901]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",-117],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1]]
Origin = (440720.000000,3751320.000000)
Pixel Size = (60.000000,-60.000000)
Corner Coordinates:
Upper Left  (  440720.000, 3751320.000) (117d38'28.21"W, 33d54'8.47"N)
Lower Left  (  440720.000, 3720600.000) (117d38'20.79"W, 33d37'31.04"N)
Upper Right (  471440.000, 3751320.000) (117d18'32.07"W, 33d54'13.08"N)
Lower Right (  471440.000, 3720600.000) (117d18'28.50"W, 33d37'35.61"N)
Center      (  456080.000, 3735960.000) (117d28'27.39"W, 33d45'52.46"N)
Band 1 Block=512x16 Type=Byte, ColorInterp=Gray

gdal_translate

The gdal_translate utility can be used to convert raster data between different formats, potentially peforming some operations like subsettings, resampling, and rescaling pixels in the process.

Usage: gdal_translate 
       [-ot {Byte/UInt16/UInt32/Int32/Float32/Float64/CInt16/
             CInt32/CFloat32/CFloat64}] [-not_strict]
       [-of format] [-b band] [-outsize xsize[%] ysize[%]]
       [-scale [src_min src_max [dst_min dst_max]]]       
       [-srcwin xoff yoff xsize ysize] [-a_srs srs_def]
       [-projwin xoff yoff xsize ysize] [-co "NAME=VALUE"]*
       src_dataset dst_dataset

• -ot: For the output bands to be of the indicated data type.
• -not_strict: Be forgiving of mismatches and lost data when translating to the output format.
• -of format: Select the output format. The default is GeoTIFF (GTiff). Use the short format name.
• -b band: Select only input band band for output. Bands are numbered from 1.
• -outsize xsize[%] ysize[%]: Set the size of the output file. Outsize is in pixels and lines unless '%' is attached in which case it is as a fraction of the input image size.
• -scale [src_min src_max [dst_min dst_max]]: Rescale the input pixels values from the range src_min to src_max to the range dst_min to dst_max. If omitted the output range is 0 to 255. If omitted the input range is automatically computed from the source data.
• -srcwin xoff yoff xsize ysize: Selects a subwindow from the source image for copying.
• -a_srs srs_def: Override the projection for the output file. The srs_def may be any of the usual GDAL/OGR forms, complete WKT, PROJ.4, EPSG:n or a file containing the wkt.
• -projwin ulx uly lrx lry: Selects a subwindow from the source image for copying (like -srcwin) but with the corners given in georeferenced coordinates.
• -mo "KEY=VALUE": passes a metadata key and value to set on the output dataset if possible.
• -co "NAME=VALUE": passes a creation option to the output format driver. Multiple -co options may be listed. See format specific documentation for legal creation options for each format.
• src_dataset: The source file name.
• dst_dataset: The destination file name.

Example:

% gdal_translate -of GTiff -co "TILED=YES" utm.tif utm_tiled.tif

gdaladdo

The gdaladdo utility can be used to build or rebuild overview images for most supported file formats with one over several downsampling algorithms.

Usage: gdaladdo [-r {nearest,average,average_mp,average_magphase,mode}]
                filename levels

Example:
 % gdaladdo -r average abc.tif 2 4 8 16

• -r {nearest,average,average_mp,average_magphase,mode}: Select a resampling algorithm.
• filename: The file to build overviews for.
• levels: A list of integral overview levels to build.

Mode is not actually implemented, and average_mp is unsuitable for use. Average_magphase averages complex data in mag/phase space. Nearest and average are applicable to normal image data. Nearest applies a nearest neighbour (simple sampling) resampler, while average computes the average of all non-NODATA contributing pixels.

Selecting a level value like 2 causes an overview level that is 1/2 the resolution (in each dimension) of the base layer to be computed. If the file has existing overview levels at a level selected, those levels will be recomputed and rewritten in place.

Some format drivers do not support overviews at all. Many format drivers store overviews in a secondary file with the extension .ovr. The GeoTIFF driver stores overviews internally to the file operated on.

gdalwarp

The gdalwarp utility is a simple image reprojection and warping utility. The program can reproject to any support projection, and can also apply GCPs stored with the image if the image is "raw" with control information.

Usage: gdalwarp [--version] [--formats]
    [-s_srs srs_def] [-t_srs srs_def] [-order n] [-et err_threshold]
    [-te xmin ymin xmax ymax] [-tr xres yres] [-ts width height]
    [-of format] [-co "NAME=VALUE"]* srcfile dstfile

• -s_srs srs def: source spatial reference set. The coordinate systems that can be passed are anything supported by the OGRSpatialReference.SetFromUserInput() call, which includes EPSG PCS and GCSes (ie. EPSG:4296), PROJ.4 declarations (as above), or the name of a .prf file containing well known text.
• -t_srs srs_def: target spatial reference set. The coordinate systems that can be passed are anything supported by the OGRSpatialReference.SetFromUserInput() call, which includes EPSG PCS and GCSes (ie. EPSG:4296), PROJ.4 declarations (as above), or the name of a .prf file containing well known text.
• -order n: order of polynom used for warping (1 to 3)
• -et err_threshold: error threshold for transformation approximation (in pixel units - defaults to 0.125).
• -te xmin ymin xmax ymax: set georeferenced extents of output file to be created.
• -tr xres yres: set output file resolution (in target georeferenced units)
• -ts width height: set output file size in pixels and lines
• -of format: Select the output format. The default is GeoTIFF (GTiff). Use the short format name.
• -co "NAME=VALUE": passes a creation option to the output format driver. Multiple -co options may be listed. See format specific documentation for legal creation options for each format.
• srcfile: The source file name.
• dstfile: The destination file name.

Mosaicing into an existing output file is supported if the output file already exists.

It currently has the following limitations:

• Only 8 bit data is can be warped.
• The entire source image is held in memory.
• Only nearest neighbour resampling is available.

Example: For instance, an eight bit spot scene stored in GeoTIFF with control points mapping the corners to lat/long could be warped to a UTM projection with a command like this:

% gdalwarp -t_srs '+proj=utm +zone=11 +datum=WGS84' raw_spot.tif utm11.tif

gdaltindex

This program builds a shapefile with a record for each input raster file, an attribute containing the filename, and a polygon geometry outlining the raster. This output is suitable for use with UMN MapServer as a raster tileindex.

Usage: gdaltindex [-tileindex field_name] index_file [gdal_file]*

eg.
  % gdaltindex doq_index.shp doq/*.tif

• The shapefile (index_file) will be created if it doesn't already exist.
• The default tile index field is 'location'.
• Raster filenames will be put in the file exactly as they are specified on the commandline.
• Simple rectangular polygons are generated in the same coordinate system as the rasters.

rgb2pct.py

This utility will compute an optimal pseudo-color table for a given RGB image using a median cut algorithm on a downsampled RGB histogram. Then it converts the image into the a pseudo-colored image using the color table. This conversion utilizes Floyd-Steinberg dithering (error diffusion) to maximize output image visual quality.

Usage: rgb2pct.py [-n colors] [-of format] source_file dest_file

• -n colors: Select the number of colors in the generated color table. Defaults to 256. Must be between 2 and 256.
• -of format: Format to generated (defaults to GeoTIFF). Same semantics as the -of flag for gdal_translate. Only output formats supporting pseudocolor tables should be used.
• source_file: The input RGB file.
• dest_file: The output pseudo-colored file that will be created.

NOTE: rgb2pct.py is a Python script, and will only work if GDAL was built with Python support. It is also not installed by default. It is found at $GDAL_HOME/pymod.

gdal_merge.py

This utility will automatically mosaic a set of images. All the images must be in the same coordinate system and have a matching number of bands, but they may be overlapping, and at different resolutions.

Usage: gdal_merge.py [-o out_filename] [-f out_format] [-v]
                     [-ps pixelsize_x pixelsize_y]
                     [-ul_lr ulx uly lrx lry] input_files

• -o out_filename: The name of the output file to be created.
• -f out_format: Output format, defaults to GeoTIFF.
• -ps pixelsize_x pixelsize_y: Pixel size to be used for the output file. If not specified the resolution of the first input file will be used.
• -ul_lr ulx uly lrx lry: The extents of the output file. If not specified the aggregate extents of all input files will be used.
• -v: Generate verbose output of mosaicing operations as they are done.

NOTE: gdal_merge.py is a Python script, and will only work if GDAL was built with Python support. It is also not installed by default. It is found at $GDAL_HOME/pymod.

gdal-config

This utility script (available on Unix systems) can be used to determine various information about a GDAL installation. It is normally just used by configure scripts for applications using GDAL but can be queried by an end user.

Usage: gdal-config [OPTIONS]
Options:
        [--prefix[=DIR]]
        [--libs]
        [--cflags]
        [--version]
        [--ogr-enabled]
        [--formats]

• --prefix: the top level directory for the GDAL installation.
• --libs: The libraries and link directives required to use GDAL.
• --cflags: The include and macro definition required to compiled modules using GDAL.
• --version: Reports the GDAL version.
• --ogr-enabled: Reports "yes" or "no" to standard output depending on whether OGR is built into GDAL.
• --formats: Reports which formats are configured into GDAL to stdout.

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