# Navigation Stack and Concepts

Source: <http://wiki.ros.org/navigation/Tutorials/Using%20rviz%20with%20the%20Navigation%20Stack>

| Section            | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| ------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 2D Nav Goal        | <p></p><ul><li>Topic: move\_base\_simple/goal</li><li>Type: <a href="http://docs.ros.org/en/api/geometry_msgs/html/msg/PoseStamped.html">geometry\_msgs/PoseStamped</a></li><li>Description: Allows the user to send a goal to the <a href="http://wiki.ros.org/navigation">navigation</a> by setting a desired pose for the robot to achieve.</li></ul>                                                                                                                                                                                             |
| 2D Pose Estimate   | <ul><li>Topic: initialpose</li><li>Type: <a href="http://docs.ros.org/en/api/geometry_msgs/html/msg/PoseWithCovarianceStamped.html">geometry\_msgs/PoseWithCovarianceStamped</a></li><li>Description: Allows the user to initialize the <a href="http://wiki.ros.org/amcl">localization system</a> used by the <a href="http://wiki.ros.org/navigation">navigation</a> stack by setting the pose of the robot in the world.</li></ul>                                                                                                                |
| Static Map         | <ul><li>Topic: map</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/srv/GetMap.html">nav\_msgs/GetMap</a></li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/OccupancyGrid.html">nav\_msgs/OccupancyGrid</a></li><li>Description: Displays the static map that is being served by the <a href="http://wiki.ros.org/map_server">map\_server</a> if one exists.</li></ul>                                                                                                                                              |
| Particle Cloud     | <ul><li>Topic: particlecloud</li><li>Type: <a href="http://docs.ros.org/en/api/geometry_msgs/html/msg/PoseArray.html">geometry\_msgs/PoseArray</a></li><li>Description: Displays the particle cloud used by the robot's <a href="http://wiki.ros.org/amcl">localization</a> system. The spread of the cloud represents the <a href="http://wiki.ros.org/amcl">localization</a> system's uncertainty about the robot's pose. A cloud that is very spread out reflects high uncertainty, while a condensed cloud represents low uncertainty.</li></ul> |
| Robot Footprint    | <ul><li>Topic: local\_costmap/robot\_footprint</li><li>Type: <a href="http://docs.ros.org/en/api/geometry_msgs/html/msg/PolygonStamped.html">geometry\_msgs/PolygonStamped</a></li><li>Description: Displays the footprint of the robot</li></ul>                                                                                                                                                                                                                                                                                                    |
| Obstacles          | <ul><li>Topic: local\_costmap/obstacles</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/GridCells.html">nav\_msgs/GridCells</a></li><li>Desctiption: Displays the obstacles that the navigation stack sees in its <a href="http://wiki.ros.org/costmap_2d">costmap</a>. For the robot to avoid collision, the robot footprint should never intersect with a cell that contains an obstacle.</li></ul>                                                                                                                            |
| Inflated Obstacles | <ul><li>Topic: local\_costmap/inflated\_obstacles</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/GridCells.html">nav\_msgs/GridCells</a></li><li>Description: Displays obstacles in the navigation stack's <a href="http://wiki.ros.org/costmap_2d">costmap</a> inflated by the inscribed radius of the robot. For the robot to avoid collision, the center point of the robot should never overlap with a cell that contains an inflated obstacle.</li></ul>                                                                   |
| Unknown Space      | <ul><li>Topic: local\_costmap/unknown\_space</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/GridCells.html">nav\_msgs/GridCells</a></li><li>Description: Displays any unknown space contained in the navigation stack's <a href="http://wiki.ros.org/costmap_2d">costmap\_2d</a>.</li></ul>                                                                                                                                                                                                                                     |
| Global Plan        | <ul><li>Topic: TrajectoryPlannerROS/global\_plan</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/Path.html">nav\_msgs/Path</a></li><li>Description: Displays the portion of the global plan that the <a href="http://wiki.ros.org/base_local_planner">local planner</a> is currently pursuing.</li></ul>                                                                                                                                                                                                                         |
| Local Plan         | <ul><li>Topic: TrajectoryPlannerROS/local\_plan</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/Path.html">nav\_msgs/Path</a></li><li>Description: Displays the trajectory associated with the velocity commands currently being commanded to the base by the <a href="http://wiki.ros.org/base_local_planner">local planner</a>.</li></ul>                                                                                                                                                                                      |
| Planner Plan       | <ul><li>Topic: TrajectoryPlannerROS/local\_plan</li><li>Type: <a href="http://docs.ros.org/en/api/nav_msgs/html/msg/Path.html">nav\_msgs/Path</a></li><li>Description: Displays the trajectory associated with the velocity commands currently being commanded to the base by the <a href="http://wiki.ros.org/base_local_planner">local planner</a>.</li></ul>                                                                                                                                                                                      |
| Current Goal       | <ul><li>Topic: current\_goal</li><li>Type: <a href="http://docs.ros.org/en/api/geometry_msgs/html/msg/PoseStamped.html">geometry\_msgs/PoseStamped</a></li><li>Description: Displays the goal pose that the navigation stack is attempting to achieve.</li></ul>                                                                                                                                                                                                                                                                                     |


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