Proj4 is a library that provides methods to transform between different coordinate reference systems. A geographic coordinate reference systems allows all points on the earth to be described as a set of coordinates (such as latitude, longitude and elevation). Different systems are used to represent the 3 dimensional earth on a flat, 2 dimensional map.

Proj4 is used as a projection tool in MapServer, GRASS GIS, PostGIS, Mapnik, Thuban, OGDI, TopoCad, OGRCoordinateTransformation and various others.

Proj4 has been translated from C to other languages. These sub-projects include:

  1. Proj4js (JavaScript) – used in OpenLayers.
  2. CS-Map (C++) – used in MapGuide.
  3. GeoTIFF/libgeotiff (C++).
  4. Proj4J (Java).
  5. – website to retrieve coordinate system definitions (obsolete).

Proj4 uses coordinate system definitions defined by the European Petroleum Survey Group (EPSG). Well Known Text (WKT) format.


Licence: X/MIT style Open Source license

Software Version: 4.9.2 (stable)

Supported Platforms: Windows, Linux, Mac

API Interfaces: C, C++, Python, Java, Ruby


Quickstart documentation

Core features

  • API

    • Provides point transformation from one coordinate reference system to another.
    • Includes transformation between datums.
    • Large number of projection classes supported.

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