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=====SLAM: Self Localization and  Mapping =====

**Prerequisite:**
  * get a running catkin environment.
  * check your environment variables.
  * check the necessary topics are up and running (''cmd_vel'', ''laser'', ''tf'',...)
  * [[ROSLaserFilter|Filter]] the LaserScan if necessary.
  * Run: roscore and robot drivers and scripts. 

----

==== gmapping ====
Even without having a map of the environment, we can create one on-the-fly, thanks to
[[http://wiki.ros.org/slam_gmapping/Tutorials|SLAM]] (Self Localization and Mapping).

You will need to set up you robot completely, then to launch ''slam_gmapping''. It may be helpful to create a launchfile to pass parameters, for example in ''gmapping.launch'':
<WRAP box >''<launch>\\
    <param name="use_sim_time" value="false"/>\\
    <node pkg="gmapping" type="slam_gmapping" name="slam_gmapping" output="screen">\\
        <!-- descriptions and defaults: \\
            http://www.ros.org/wiki/gmapping#Parameters   -->\\        
        <param name="xmin" value="-5.0"/>\\
        <param name="ymin" value="-5.0"/>\\
        <param name="xmax" value="5.0"/>\\
        <param name="ymax" value="5.0"/>\\
        <param name="maxUrange" value="59.0"/><!--60! ?-->\\
        <param name="maxRange" value="63.0"/>\\
        
        <param name="map_update_interval" value="5.0"/> <!-- def -->\\
        <param name="linearUpdate" value="0.2"/>\\
        <param name="angularUpdate" value="0.15"/>\\
        <param name="particles" value="50"/>\\
        
        <param name="delta" value="0.1"/>\\
    </node>\\
</launch> '' </WRAP>

Then, launch ''rviz'' and see the result, published in topic ''/map''.

----
==== Hector Slam====
  * This [[http://wiki.ros.org/hector_slam|metapackage]] is part of the [[http://wiki.ros.org/tu-darmstadt-ros-pkg|TU Darmstadt]] repository.
  * To install it in Debian/Ubuntu:  <WRAP box 350px>''sudo apt-get install ros-hydro-hector-slam'' </WRAP>
  * For mapping, we're intested in the [[http://wiki.ros.org/hector_mapping|hector_mapping]] package.

----
====Working offline with a "bag" of data====
One may need to first record the data before computing the map. That is possible, with a "bag".

See the tutorial [[http://wiki.ros.org/slam_gmapping/Tutorials/MappingFromLoggedData]]

One first needs to make a bag of data, e.g.:  <WRAP box 350px>''rosbag record -O mylaserdata /scan /tf'' </WRAP>