NAME

       gdal_merge - Mosaics a set of images.

SYNOPSIS

          gdal_merge [--help] [--help-general]
                        [-o <out_filename>] [-of <out_format>] [-co <NAME>=<VALUE>]...
                        [-ps <pixelsize_x> <pixelsize_y>] [-tap] [-separate] [-q] [-v] [-pct]
                        [-ul_lr <ulx> <uly> <lrx> <lry>] [-init "<value>[ <value>]..."]
                        [-n <nodata_value>] [-a_nodata <output_nodata_value>]
                        [-ot <datatype>] [-createonly] <input_file> [<input_file>]...

DESCRIPTION

       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. In
       areas of overlap, the last image will  be  copied  over  earlier  ones.  Nodata/transparency  values  are
       considered  on  a  band  by band level, i.e. a nodata/transparent pixel on one source band will not set a
       nodata/transparent value on all bands for the target pixel in the resulting raster nor will it  overwrite
       a valid pixel value.

       NOTE:
          gdal_merge is a Python utility, and is only available if GDAL Python bindings are available.

       --help Show this help message and exit

       --help-general
              Gives a brief usage message for the generic GDAL commandline options and exit.

       -o <out_filename>
              The  name  of  the  output  file,  which will be created if it does not already exist (defaults to
              "out.tif").

       -of <format>
              Select the output format. If not specified, the format is guessed  from  the  extension.  Use  the
              short format name.

       -co <NAME>=<VALUE>
              Many  formats  have  one or more optional creation options that can be used to control particulars
              about the file created. For instance, the GeoTIFF driver  supports  creation  options  to  control
              compression, and whether the file should be tiled.

              The  creation  options  available  vary by format driver, and some simple formats have no creation
              options at all. A list of options supported for a format can be listed with the  --format  command
              line option but the documentation for the format is the definitive source of information on driver
              creation options.  See Raster drivers format specific documentation for legal creation options for
              each format.

       -ot <type>
              Force  the  output  image bands to have a specific data type supported by the driver, which may be
              one of the following: Byte, Int8, UInt16, Int16, UInt32, Int32, UInt64, Int64,  Float32,  Float64,
              CInt16, CInt32, CFloat32 or CFloat64.

       -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.

       -tap   (target aligned pixels) align the coordinates of the extent of the output file to  the  values  of
              the  -tr,  such  that the aligned extent includes the minimum extent.  Alignment means that xmin /
              resx, ymin / resy, xmax / resx and ymax / resy are integer values.

       -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.

       -q, -quiet
              Suppress progress messages.

       -v     Generate verbose output of mosaicing operations as they are done.

       -separate
              Place each input file into a separate band.

       -pct   Grab a pseudo-color table from the first  input  image,  and  use  it  for  the  output.   Merging
              pseudo-colored images this way assumes that all input files use the same color table.

       -n <nodata_value>
              Ignore pixels from files being merged in with this pixel value.

       -a_nodata <output_nodata_value>
              Assign a specified nodata value to output bands.

       -init <"value(s)">
              Pre-initialize  the output image bands with these values.  However, it is not marked as the nodata
              value in the output file.  If only one value is given, the same value is used in all the bands.

       -createonly
              The output file is created (and potentially pre-initialized) but no input  image  data  is  copied
              into it.

EXAMPLES

   Example 1: Creating an image with the pixels in all bands initialized to 255
          gdal_merge -init 255 -o out.tif in1.tif in2.tif

   Example 2: Creating an RGB image that shows blue in pixels with no data
          gdal_merge -init "0 0 255" -o out.tif in1.tif in2.tif

       The first two bands will be initialized to 0 and the third band will be initialized to 255.

   Example 3: Passing a large list of files to gdal_merge
          ls -1 *.tif > tiff_list.txt

       A  large list of files can be passed to gdal_merge by listing them in a text file using the command above
       on Linux, or:

          dir /b /s *.tif > tiff_list.txt

       on Windows. The text file can then be passed to gdal_merge using --optfile:

          gdal_merge -o mosaic.tif --optfile tiff_list.txt

   Example 4: Creating an RGB image by merging 3 different greyscale bands
       Conduct "merging by stacking" with the -separate flag. Given three greyscale files that  cover  the  same
       area, you can run:

          gdal_merge -separate 1.tif 2.tif 3.tif -o rgb.tif

       This maps 1.tif to red, 2.tif to green and 3.tif to blue.

   Example 5: Specifying overlap precedence
       The  last  image  in the input line comes out on top of the finished image stack.  You might also need to
       use -n to note which value should not be copied into the destination image if it is not  already  defined
       as nodata.

          gdal_merge -o merge.tif -n 0 image1.tif image2.tif image3.tif image4.tif

AUTHOR

       Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>

COPYRIGHT

       1998-2025

                                                  Nov 07, 2025                                     GDAL_MERGE(1)