.. _coordinate_systems:

Coordinate Systems
==================

Below are the most common coordinate systems used. In addition to those each sensor usually has its own coordinate system too.

Base Link (base_link)
---------------------

The platform's own coordinate system, usually the center of mass. X points forward, Y points to the left and Z points upwards.
The internal name is ``base_link``.

Odometry (odom)
---------------

This is an arbitrary coordinate system with it's origin at the starting position (at the time of power on) of the platform.
X and Y form the plane of movement, while Z is pointing upwards and aligned with gravity. Usually there is no motion in Z direction,
except when a roll and pitch sensor is installed.
The internal name is ``odom``.

Map (map)
---------

This is the coordinate system of the currenly used :ref:`GridMap` and :ref:`RoadMap`.
Usually the :ref:`GridMap` is created first and it's origin is the starting position of where the map was created initially.
X and Y form the plane of movement, while Z is pointing upwards and aligned with gravity.
The internal name is ``map``.