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GEOS -- Geometry Engine, Open Source

GEOS is a C++ library for performing operations on two-dimensional vector geometries. It is primarily a port of the JTS Topology Suite Java library. It provides many of the algorithms used by PostGIS, the Shapely package for Python, the sf package for R, and others.

More information is available the project homepage.

The official Git repository is at GitHub.

Build Status

CI Status CI Status CI Status
GitHub github Bessie bessie Debbie debbie
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Community Resources


See the INSTALL file.

Reference Docs

See also the C API tutorial and the C++ API tutorial. There are code examples in the code repository.

Client Applications

Using the C interface

GEOS promises long-term stability of the C API. In general, successive releases of the C API may add new functions but will not remove or change existing types or function signatures. The C library uses the C++ interface, but the C library follows normal ABI-change-sensitive versioning, so programs that link only against the C library should work without relinking when GEOS is upgraded. For this reason, it is recommended to use the C API for software that is intended to be dynamically linked to a system install of GEOS.

The geos-config program can be used to determine appropriate compiler and linker flags for building against the C library:

CFLAGS += `geos-config --cflags`
LDFLAGS += `geos-config --ldflags` -lgeos_c

All functionality of the C API is available through the geos_c.h header file.

Documentation for the C API is provided via comments in the geos_c.h header file. C API usage examples can be found in the GEOS unit tests and in the source code of software that uses GEOS, such as PostGIS and the sf package for R.

Using the C++ interface

The C++ interface to GEOS provides a more natural API for C++ programs, as well as additional functionality that has not been exposed in the C API. However, developers who decide to use the C++ interface should be aware that GEOS does not promise API or ABI stability of the C++ API between releases. Breaking changes in the C++ API/ABI are not typically announced or included in the NEWS file.

The C++ library name will change on every minor release.

The geos-config program can be used to determine appropriate compiler and linker flags for building against the C++ library:

CFLAGS += `geos-config --cflags`
LDFLAGS += `geos-config --ldflags` -lgeos

A compiler warning may be issued when building against the C++ library. To remove the compiler warning, define USE_UNSTABLE_GEOS_CPP_API somewhere in the program.

Commonly-used functionality of GEOS is available in the geos.h header file. Less-common functionality can be accessed by including headers for individual classes, e.g. #include <geos/algorithm/distance/DiscreteHausdorffDistance.h>.

#include <geos.h>

C++ usage examples can be found in examples.

Using other languages

GEOS has bindings in many languages, see the bindings page.


API documentation can be generated using Doxygen. Documentation is not included in the default build. To build the documentation, run:

cmake --build . --target docs


To format your code into the desired style, use the astyle version included in source tree:

tools/ <yourfile.cpp>


See documentation in tests/