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What is the meaning of <rayCount>, <rangeCount> and <laserCount> for laser sensor XML?

asked 2012-12-23 23:03:32 -0500

ChengXiang gravatar image

updated 2012-12-26 03:51:23 -0500

Hi, I am using simulating a laser sensor. However, I have some doubts about the meaning of some tags in the xml description. Even the ROS web page do not provide information on this.

The xml description look something like this

<gazebo reference="base_scan_link">
            <sensor:ray name="laser">
                <rayCount>683</rayCount>
                <rangeCount>683</rangeCount>
                <laserCount>1</laserCount>

                <origin>0.0 0.0 0.0</origin>
                <displayRays>false</displayRays>

                <minAngle>-135</minAngle>
                <maxAngle> 135</maxAngle>

                <minRange>0.06</minRange>
                <maxRange>4.0</maxRange>
                <resRange>0.001</resRange>
                <updateRate>10.0</updateRate>

                <controller:gazebo_ros_laser 
name="gazebo_ros_base_scan_link_controller" plugin="libgazebo_ros_laser.so">
                    <gaussianNoise>0.005</gaussianNoise>
                    <alwaysOn>true</alwaysOn>
                    <updateRate>10.0</updateRate>
                    <topicName>base_scan/scan</topicName>
                    <frameName>base_scan_link</frameName>
                    <interface:laser name="gazebo_ros_base_scan_link_iface"/>
                </controller:gazebo_ros_laser>
            </sensor:ray>
        </gazebo>

I wish to know what are the function of <raycount>, <rangecount>,<lasercount> and Gaussian noise. Can anyone explain what are the meanings of the above mentioned tags? Thank you.

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Please provide more information. What web page are you looking at? What xml file are you trying to write?

tfoote gravatar image tfoote  ( 2012-12-24 04:37:31 -0500 )edit

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answered 2012-12-26 23:24:47 -0500

Chad Rockey gravatar image

This page has information on the actual xml structure: http://answers.ros.org/question/44691/how-to-put-hokuyo-laser-sensor-on-p2os/

As for those meanings, I found some information here on rangecount and raycount: http://osdir.com/ml/science.robotics.playerstage.gazebo/2008-08/msg00044.html

rangecount is the amount of data to export. Raycount is the number of rays to simulate in gazebo. Since these can be computationally expensive, each rangecount will be interpolated to the nearest raycount if raycount < rangecount. For best sensor simulation, raycount = rangecount.

There's no clear use for lasercount anywhere, other than 1. I'd assume it's the number of planar lasers, the number of stacked lasers, or the number of returns.

Finally, the Gaussian noise is the amount of simulated noise to add to each reading. Gazebo supports "noisy" data by adding data in a distribution with that number as the variance.

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Thank you for the information, they are very helpful.

ChengXiang gravatar image ChengXiang  ( 2012-12-27 03:35:31 -0500 )edit

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Asked: 2012-12-23 23:03:32 -0500

Seen: 256 times

Last updated: Dec 26 '12