Prepare with gdal_retile

Introduction to

Attention: These examples were executed on a linux, box, if you have a Microsoft platform, you must change your path names. Additionally, the executable is gdal_retile.bat instead of

The following examples assume we have a big image called big.tif.

  • First simple example: -targetDir /tmp/test  big.tif
    Result: In the directory /temp/test are many georeferenced tiles,  pixelsize 256x256, which will mosaic to the original image.
  • Example of specific size: -ps 512 512 -targetDir /tmp/test big.tif

    Result: The tiles are 512 pixel x 512 pixel

  • Sometimes you need to specify the coordinate system: -s_srs EPSG:4326 -ps 512 512 -targetDir /tmp/test  big.tif
  • Now, we build additional pyramids: -levels 3 -ps 512 512 -targetDir /tmp/test big.tif

    Result: There are 3 additional subdirectories /tmp/test/1,/tmp/test/2,/tmp/test/3 containing the tiles for 3 pyramid levels.

  • If we have already a set of tiles (*.tif) and need only the tiled pyramids: -levels 3 -pyramidOnly -ps 512 512 -targetDir /tmp/test *.tif
  • If we have already a set of tiles (*.tif or *.png or …) and need to retile and to build pyramids: -levels 3  -ps 512 512 -targetDir /tmp/test *.tif
  • There some more switches (e.g. image format ), please consult the man page.

Common problems:

  • If you have many tiles , the *.tif pattern could result in a “command line buffer exceeded” error. This is not a problem of the utility.

    In this situation you have to create a file listing all the tif files with absolute path names (Lets call it tilelist.txt ) and then change the above command to: -levels 3  -ps 512 512 -targetDir /tmp/test --optfile tilelist.txt

Exporting the georeferencing information

Now we can decide how to prepare the georeferencing information:

  • Exporting the georeferencing information into a csv file: -levels 3  -ps 512 512 -csv index.csv -targetDir /tmp/test --optfile tilelist.txt

    This produces a csv file for for each image level.

    • The csv has 5 columns: filename,minx,maxx,miny,maxy.
    • Each record describes the georeferencing information for a tile.
  • Exporting the georeferencing information into a shape file: -levels 3  -ps 512 512 -tileIndex index.shp -tileIndexField LOCATION -targetDir /tmp/test --optfile tilelist.txt

    This produces shape files named index.shp with a geometry attribute LOCATION. Use to check the content.

  • Exporting the georeferencing information into world files: -levels 3  -ps 512 512 -co "WORLDFILE=YES" -targetDir /tmp/test --optfile tilelist.txt