About

PROJ is a generic coordinate transformation software that transforms geospatial coordinates from one coordinate reference system (CRS) to another. This includes cartographic projections as well as geodetic transformations. PROJ is released under the X/MIT open source license

PROJ includes command line applications for easy conversion of coordinates from text files or directly from user input. In addition to the command line utilities PROJ also exposes an application programming interface, or API in short. The API lets developers use the functionality of PROJ in their own software without having to implement similar functionality themselves.

PROJ started purely as a cartography application letting users convert geodetic coordinates into projected coordinates using a number of different cartographic projections. Over the years, as the need has become apparent, support for datum shifts has slowly worked its way into PROJ as well. Today PROJ supports more than a hundred different map projections and can transform coordinates between datums using all but the most obscure geodetic techniques.

Citation

To cite PROJ in publications use:

PROJ contributors (2020). PROJ coordinate transformation software library. Open Source Geospatial Foundation. URL https://proj.org/. DOI: 10.5281/zenodo.5884394

A BibTeX entry for LaTeX users is

@Manual{,
  title = {{PROJ} coordinate transformation software library},
  author = {{PROJ contributors}},
  organization = {Open Source Geospatial Foundation},
  year = {2022},
  url = {https://proj.org/},
  doi = {10.5281/zenodo.5884394},
}

License

PROJ uses the MIT license. The software was initially released by the USGS in the public domain. When Frank Warmerdam took over the development of PROJ it was moved under the MIT license. The full text of the license follows, and can also be found in the file COPYING, at the top level of the source distribution package.

All source, data files and other contents of the PROJ package are 
available under the following terms.  Note that the PROJ 4.3 and earlier
was "public domain" as is common with US government work, but apparently
this is not a well defined legal term in many countries. Frank Warmerdam placed
everything under the following MIT style license because he believed it is
effectively the same as public domain, allowing anyone to use the code as
they wish, including making proprietary derivatives.

Initial PROJ 4.3 public domain code was put as Frank Warmerdam as copyright
holder, but he didn't mean to imply he did the work. Essentially all work was
done by Gerald Evenden.

Copyright information can be found in source files.

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 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
 to deal in the Software without restriction, including without limitation
 the rights to use, copy, modify, merge, publish, distribute, sublicense,
 and/or sell copies of the Software, and to permit persons to whom the
 Software is furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included
 in all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.