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Visualization of the maximum distance point in rviz

asked 2012-08-07 16:39:15 -0500

Astronaut gravatar image

updated 2012-08-08 00:27:16 -0500

dornhege gravatar image


I create and build own node that calculate the maximal distance of the obstacle (based on laser data). I would like to visualize that point in rviz and distinguished with some colour(for example green). This is my launch file

<param name="/use_sim_time" value="true"/>

<node name="rosplay" pkg="rosbag" type="play" args=" /Data/p1-20.bag --loop  --clock"/>

<node pkg="tf" type="static_transform_publisher" name="baselink_laser" args="0 0 0 0 0 0 /base_link /laser 10"/>
<node pkg="tf" type="static_transform_publisher" name="laser_imu" args="0 0 0 0 0 0 /laser /base_imu 10"/>
<node pkg="tf" type="static_transform_publisher" name="baselink_camera" args="0 0 0 0 0 0 /base_link /camera 10"/>

<!-- Start the map server node and specify the map file (*.pgm) and the map resolution in metres/pixel -->
<node name="map_server" pkg="map_server" type="map_server" args="$(find amcl_listener)/maps/pow_real_time.yaml"         output="screen"/>

<!--Start the Laser_scan_matcher package, to provide odometry from laser data (ICP)-->
<node pkg="laser_scan_matcher" type="laser_scan_matcher_node" 
    name="laser_scan_matcher_node" output="screen">
    <param name="use_alpha_beta" value="true"/>
    <param name="max_iterations" value="10"/>

<node pkg="amcl" type="amcl" name="amcl" respawn="true" output="screen">
    <param name="base_frame_id" value="base_link"/>
    <param name="odom_frame_id" value="world"/>
    <param name="global_frame_id" value="map"/>
    <param name="update_min_d" value="0.09"/>   
    <param name="update_min_a" value="0.09"/> 
    <param name="initial_pose_x" value="-1"/>
    <param name="initial_pose_y" value="0"/>
    <param name="initial_pose_a" value="-0.1"/>
    <param name="min_particles" value="6000"/> 
    <param name="max_particles" value="8000"/>
    <param name="odom_model_type" value="diff"/>
    <param name="kld_err" value="0.1"/> 
    <param name="resample_interval" value="1"/>
    <param name="odom_alpha1" value="0.2"/>   
    <param name="odom_alpha2" value="0.2"/>
    <param name="odom_alpha3" value="0.5"/>
    <param name="odom_alpha4" value="0.5"/>
    <param name="laser_max_beams" value="30"/>

<!--Start the "analyzer_packages"-->
<!-- acml_listener broadcasts markers for the position of the wheelchair, to visualize in Rviz-->
<node pkg="amcl_listener" type="amcl_pose_listener" name="amcl_listener" output="screen"/>
<!-- Object node records minimal ranges from laser, speed_node will record travel speed of wheelchair -->
<!--node pkg="pow_analyzer" type="object_node" name="object_node" output="screen"/> -->
<node pkg="pow_analyzer" type="max_range_node" name="max_range_node" output="screen"/>
<!--node pkg="pow_analyzer" type="speed_node" name="speed_node" output="screen"/> -->

<!-- Start an rviz node with a custom configuration for the viewpoint, map_server, trajectory, laser scans, etc -->
<node pkg="rviz" type="rviz" output="screen" name="rviz" args="-d $(find pow_analyzer)/launch/pow_rviz.vcg"/> 


This is the source code of the max_range_node

#include "ros/ros.h"
#include "std_msgs/String.h"
#include "sensor_msgs/LaserScan.h"
#include <vector>

sensor_msgs::LaserScan laser_scan;
float min_range;
float max_range;

void scanCallback(const sensor_msgs::LaserScan::ConstPtr& msg)

    std::vector<float> laser;
    laser = msg->ranges;

    int size_laser = laser.size();
    for (int i=0;i<size_laser;i++){
        if (laser[i] < 0.01){
            laser[i] = 99999;
        if (laser[i] > 45){
            laser[i] = 99999;

    min_range = 2; //Init closest point 
    max_range = 1; // Init maximal distance point
    int index_min; 
    int index_max; 

//find the closest point to the obstacle and the maximal distance to the //obstacle

    for (int i=0;i<size_laser;i++){
        for (int j=0;j<size_laser;j++){

        if (laser[i] < min_range ...
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What is max_range_node doing and how does it provide its data? What's the output of rosnode info max_range_node? By just seeing the launch file, it is hard to infer what all your nodes are doing without even having the documentation/sourcecode of these nodes.

Lorenz gravatar image Lorenz  ( 2012-08-07 22:37:41 -0500 )edit

Ok. Just add the source code of the node. Max range just calculate the max distance of the obstacle of the laser range scan data,.

Astronaut gravatar image Astronaut  ( 2012-08-07 22:45:53 -0500 )edit

I just want to mark (with some colour, for example green) this Maximum range, which is max_range calculated in the node I just post it.

Astronaut gravatar image Astronaut  ( 2012-08-07 22:52:55 -0500 )edit

I just the max_range_node visualize. The other nodes are at the moment not important. Ok?

Astronaut gravatar image Astronaut  ( 2012-08-07 23:04:54 -0500 )edit

Your code seems quite obscure. Are you sure it does what you want? You walk over the laser in nested loops. If you just want to get the max/min that is wrong.

dornhege gravatar image dornhege  ( 2012-08-08 02:09:00 -0500 )edit

Ok. yes than its wrong. What should I do to get max/min?

Astronaut gravatar image Astronaut  ( 2012-08-09 22:02:24 -0500 )edit

Well, usually it's: max=0; for(uint i ... laser.range) if(laser.range[i] > max: max=laser.range[i]

dornhege gravatar image dornhege  ( 2012-08-10 02:54:08 -0500 )edit

1 Answer

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answered 2012-08-08 00:26:28 -0500

dornhege gravatar image

Given your purpose I'd suggest to use a visualization_msgs/Marker instead of a LaserScan. A LaserScan can only display complete data, not single beams. With a marker, you can choose specific points, select a color, and also increase the size of the marker.

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Ok. Thanks. How to use a visualization_msgs/Marker??Where to specify that?Do I need some extra code for the marker???

Astronaut gravatar image Astronaut  ( 2012-08-08 01:18:54 -0500 )edit

any example of visualization_msgs/Marker and single beam like maximum range??

Astronaut gravatar image Astronaut  ( 2012-08-08 01:49:36 -0500 )edit

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Asked: 2012-08-07 16:39:15 -0500

Seen: 1,075 times

Last updated: Aug 08 '12