# Probability occupancy grid with Turtlebot's Gmapping?

Anonymous

Kinetic, Ubuntu 16.04

Turtlebot3 using Gmapping

Gmapping uses a threshold to turn its maps into a binary map of cells that have either 'occupied' or 'free' (or 'unknown'). However, I need to use the probabilistic occupancy grid map with its full range of values. I've looked around the code, and previous answers

The problem is that I don't have a gmapping package; I have a turtlebot3 package. I can't find code where it applies the treshold to a probability map to turn it into a binary map. I just have files like:

<launch>
<!-- Turtlebot3 -->
<include file="$(find turtlebot3_bringup)/launch/turtlebot3_remote.launch" /> <!-- Gmapping --> <node pkg="gmapping" type="slam_gmapping" name="turtlebot3_slam_gmapping" output="screen"> <param name="base_frame" value="base_footprint"/> <param name="odom_frame" value="odom"/> <param name="map_update_interval" value="2.0"/> <param name="maxUrange" value="8.0"/> <param name="minimumScore" value="100"/> <param name="linearUpdate" value="0.2"/> <param name="angularUpdate" value="0.2"/> <param name="temporalUpdate" value="0.5"/> <param name="delta" value="0.05"/> <param name="lskip" value="0"/> <param name="particles" value="120"/> <param name="sigma" value="0.05"/> <param name="kernelSize" value="1"/> <param name="lstep" value="0.05"/> <param name="astep" value="0.05"/> <param name="iterations" value="5"/> <param name="lsigma" value="0.075"/> <param name="ogain" value="3.0"/> <param name="srr" value="0.01"/> <param name="srt" value="0.02"/> <param name="str" value="0.01"/> <param name="stt" value="0.02"/> <param name="resampleThreshold" value="0.5"/> <param name="xmin" value="-10.0"/> <param name="ymin" value="-10.0"/> <param name="xmax" value="10.0"/> <param name="ymax" value="10.0"/> <param name="llsamplerange" value="0.01"/> <param name="llsamplestep" value="0.01"/> <param name="lasamplerange" value="0.005"/> <param name="lasamplestep" value="0.005"/> </node> </launch>  and <launch> <arg name="model" default="$(env TURTLEBOT3_MODEL)" doc="model type [burger, waffle, waffle_pi]"/>

<include file="$(find turtlebot3_bringup)/launch/includes/description.launch.xml"> <arg name="model" value="$(arg model)" />
</include>

<node pkg="robot_state_publisher" type="robot_state_publisher" name="robot_state_publisher" output="screen">
<param name="publish_frequency" type="double" value="50.0" />
</node>
</launch>


(Lots of files, I cant post all of the files in here, but can add if required)

I was told by my supervisor that I should be able to get the probability maps "in two or three lines of code", but remain in the dark as to how to go about it. I can't seem to find where Turtlebot's Gmapping is storing these probability maps / topics.

How do I get the probability maps?

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roscd gmapping

will take you to the package source directory. However if you installed only the binaries, you might want to get the source code from git.

You can now edit the source code accordingly(in your case, slam_gmapping.cpp) and perform a catkin_make.

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