Orekit can be built from source using several different tools.
All these tools are Java based and can run on many different operating systems, including Unix, GNU/Linux, Windows and Mac OS X. Some GNU/Linux distributions provide these tools in their packages repositories.
Maven is a build tool that goes far beyond simply compiling and packaging a product. It is also able to resolve dependencies (including downloading the appropriate versions from the public repositories), to run automated tests, to launch various checking tools and to create a web site for a project. It runs on any platform supporting Java.
For systems not providing maven as a package, maven can be downloaded from its site at the Apache Software Foundation. This site also explains the installation procedure.
As with all maven enabled projects, building Orekit is straightforward, simply run:
mvn assembly:single
The preceding command will perform all dependencies retrieval, compilation, tests and packaging for you. At the end, it will create several files named target/orekit-x.y.jar where x.y is the version number.
If you need to configure a proxy server for dependencies retrieval, see the Guide to using proxies page at the maven site.
If you already use maven for your own projects (or simply eclipse, see below), you may want to install Orekit in your local repository. This is done with the following command:
mvn install
For other commands like generating the site, or generating the checkstyle, findbugs or jacoco reports, see the maven plugins documentation at maven site.
Eclipse is a very rich Integrated Development Environment (IDE). It is a huge product and not a simple build tool.
For systems not providing eclipse as a package, it can be downloaded from its site at the Eclipse Foundation.
The simplest way to use Orekit with Eclipse is to follow these steps:
unpack the distribution inside your Eclipse workspace
create a new java project from existing sources and direct Eclipse to the directory where you unpacked Orekit
set the source folders to
in the source tab of the Configure Build Path dialog
set the external libraries to JRE system library (provided by Eclipse), Junit 4.x (provided by Eclipse) and Apache Commons Math (available at Apache Software Foundation Commons Math downloads page) in the libraries tab of the Configure Build Path dialog