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Why there is no tf data and no messages in odom topic?

asked 2018-11-03 10:41:59 -0600

stevemartin gravatar image


I have created my odom topic as I want to use the simulation without the gazebo. Basically, I wrote this code using tf2, that publishes transform from odom to base_link (I do have a base_link) and also publishes 0 data to the odom topic. Everything works great if I turn on the gazebo but nothing when i try to publish odom myself without gazebo:

#include <ros/ros.h>
#include <nav_msgs/Odometry.h>
#include <tf2_ros/transform_broadcaster.h>
#include <tf2/LinearMath/Quaternion.h>
#include <geometry_msgs/TransformStamped.h>

int main(int argc, char** argv){
    ros::init(argc, argv, "odometry_publisher");

    ros::NodeHandle n;
    ros::Publisher odom_pub = n.advertise<nav_msgs::Odometry>("odom", 10);
    tf2_ros::TransformBroadcaster odom_broadcaster;

    double x = 0.0;
    double y = 0.0;
    double th = 0.0;

    double vx = 0.0;
    double vy = 0.0;
    double vth = 0.0;

    ros::Time current_time, last_time;
    current_time = ros::Time::now();
    last_time = ros::Time::now();

    ros::Rate r(50.0);


        current_time = ros::Time::now();

        double dt = (current_time-last_time).toSec();
        double delta_x = (vx * cos(th) - vy * sin(th)) * dt;
        double delta_y = (vx * sin(th) + vy * cos(th)) * dt;
        double delta_th = vth * dt;

        x += delta_x;
        y += delta_y;
        th += delta_th;

        // Setting the transform stamped messages:
        tf2::Quaternion q;
        geometry_msgs::TransformStamped odom_trans;
        odom_trans.header.stamp = current_time;
        odom_trans.header.frame_id = "odom";
        odom_trans.child_frame_id = "base_link";

        odom_trans.transform.translation.x = x;
        odom_trans.transform.translation.y = y;
        odom_trans.transform.translation.z = 0.0;
        odom_trans.transform.rotation.x = q.x();
        odom_trans.transform.rotation.y = q.y();
        odom_trans.transform.rotation.z = q.z();
        odom_trans.transform.rotation.w = q.w();

        // Send the transform:

        // Send the odometry messages to ROS:
        nav_msgs::Odometry odom;
        odom.header.stamp = current_time;
        odom.header.frame_id = "odom";
        // Here, take the positions from the wheelme backend whenever it reaches and send it to ros:
        odom.pose.pose.position.x = x;
        odom.pose.pose.position.y = y;
        odom.pose.pose.position.z = 0.0;
        odom.pose.pose.orientation.x = q.x();
        odom.pose.pose.orientation.x = q.y();
        odom.pose.pose.orientation.x = q.z();
        odom.pose.pose.orientation.x = q.w();

        // This values will be always zero until wheelme will start publishing its velocities:
        odom.child_frame_id = "base_link";
        odom.twist.twist.linear.x = vx;
        odom.twist.twist.linear.y = vy;
        odom.twist.twist.angular.z  = vth;

        // Now publish all that to odom topic:
        last_time = current_time;



When I check /odom topic nothing is there, no messages and when I do rosrun tf view_frames I get no tf data.

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1 Answer

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answered 2018-11-03 10:49:01 -0600

stevemartin gravatar image

Nevermind guys, I just found my mistake. If anyone will face this problem just turn the use_sim_time to false in launch file like that:

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

It actually makes sense, as gazebo publishes its simulated clock and if you turn it off, you have to use your host machine clock

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Asked: 2018-11-03 10:41:59 -0600

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Last updated: Nov 03 '18