Computational geometry and spatial indexing on the sphere
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jmr BN_ext_count_low_zero_bits: Use CHECK
Use CHECK instead of DCHECK in the OpenSSL 1.1 version of
BN_ext_count_low_zero_bits.  Without this fix, copying the
bytes out of the BIGNUM only happened in debug mode.

Fixes #47.
Latest commit b8c45b5 Oct 15, 2018

README.md

S2 Geometry Library

Build Status

Overview

This is a package for manipulating geometric shapes. Unlike many geometry libraries, S2 is primarily designed to work with spherical geometry, i.e., shapes drawn on a sphere rather than on a planar 2D map. This makes it especially suitable for working with geographic data.

If you want to learn more about the library, start by reading the overview and quick start document, then read the introduction to the basic types.

S2 documentation can be found on s2geometry.io.

Requirements for End Users

On Ubuntu, all of these can be installed via apt-get:

sudo apt-get install cmake libgflags-dev libgoogle-glog-dev libgtest-dev libssl-dev

Otherwise, you may need to install some from source.

On macOS, use MacPorts or Homebrew. For MacPorts:

sudo port install cmake gflags google-glog openssl

Do not install gtest from MacPorts; instead download release 1.8.0, unpack, and substitute

cmake -DGTEST_ROOT=/...absolute path to.../googletest-release-1.8.0/googletest ..

in the build instructions below.

Thorough testing has only been done on Ubuntu 14.04.3 and macOS 10.12.

Build and Install

You may either download the source as a ZIP archive, or clone the git repository.

Via ZIP archive

Download ZIP file

cd [parent of directory where you want to put S2]
unzip [path to ZIP file]/s2geometry-master.zip
cd s2geometry-master

Via git clone

cd [parent of directory where you want to put S2]
git clone https://github.com/google/s2geometry.git
cd s2geometry

Building

From the appropriate directory depending on how you got the source:

mkdir build
cd build
# You can omit -DGTEST_ROOT to skip tests; see above for macOS.
cmake -DGTEST_ROOT=/usr/src/gtest ..
make
make test  # If GTEST_ROOT specified above.
sudo make install

Enable gflags and glog with cmake -DWITH_GFLAGS=ON -DWITH_GLOG=ON ....

Disable building of shared libraries with -DBUILD_SHARED_LIBS=OFF.

Python

If you want the Python interface, you will also need:

  • SWIG (for Python support, optional)

which can be installed via

sudo apt-get install swig

or on macOS:

sudo port install swig

Expect to see some warnings if you build with swig 2.0.

Other S2 implementations

  • Go (Approximately 40% complete.)
  • Java (Older version; last updated in 2011.)

Disclaimer

This is not an official Google product.