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World Plus Image

To add a normal image, for example a jpg or a gif, you will need to provide a world file, a small text file that says where the corners of the image is.

This page specifically covers the combination of a normal image format with a “world” file. A few image formats have well known ways of encoding location information in the image “metadata” fields. As an example a TIFF file with spatial metadata is known as a GeoTIFF.

Image Files

An image file is recognized as being in the “World plus Image” format if it is part of a file set consisting of the following:

  Example Description
Image File filename.jpeg Contains the raster data
World File filename.jgw contains the “world file” information letting us know where to draw the raster on the map
PRJ File filename.prj Optional file that defines the coordinates used in the “world file” above

World and Projection Files for an Image

The extension of a world file is the first and last letters of the image extension with w appended at the end.

Format Files
JEPG jpeg, jgw with optional prj
TIFF tiff, tfw with optional prj

The contents of a world file are as follows:

Line Example Definition
1 0.0359281435 Horizontal scale for a pixel
2 0.0000000000 Rotation for row, usually zero
3 0.0000000000 Rotation for column, usually zero
4 -0.0359281437 Vertical scale for pixel, usually negative as rasters count down from the upper left corner
5 -179.9820349282 Translation, usually “easting” location of the upper left pixel (ie column 0)
6 89.9820359281 Translation, usually “northing” location of the upper left pixel (ie row 0)

The Translation information can be thought of as the location of the upper left pixel, this locaiton is provided in the units of the projections being used:

  • For lat/long this location should be in the range -180,180 -90,90
  • If your image is not in lat/long you will have to include a .prj file, which is a text file with the WKT definition of the coordinate system that should be used.

JPEG Example:

If your image is world.jpg then you need a world.jgw file and optionally a world.prj file.

An example world.jgw


An example world.prj is:

GEOGCS[“GCS_WGS_1984”, DATUM[“WGS_1984”, SPHEROID[“WGS_1984”,6378137,298.257223563]], PRIMEM[“Greenwich”,0], UNIT[“Degree”,0.017453292519943295]]

Related reference

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