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2016-12-27 08:35:46 -0500 asked a question Why is it necessary to declare ros transform broadcaster in main?

Hi, I was trying to broadcast a tf in ros.

#include <ros/ros.h>
#include <tf/transform_broadcaster.h>
#include <tf/tf.h>
#include <geometry_msgs/TransformStamped.h> 

ros::Timer robot_pose_broadcaster;

void robotPoseCallBack(const ros::TimerEvent& eventalpha)
    tf::TransformBroadcaster robotPoseBroadcaster;
    geometry_msgs::TransformStamped robotPose;

    robotPose.header.stamp = ros::Time::now();
    robotPose.header.frame_id = "/map";
    robotPose.child_frame_id = "/base_link";

    robotPose.transform.translation.x = 0.0;
    robotPose.transform.translation.y = 0.0;
    robotPose.transform.translation.z = 0.0;
    robotPose.transform.rotation.x = 0.0;
    robotPose.transform.rotation.y = 0.0;
    robotPose.transform.rotation.z = 0.0;
    robotPose.transform.rotation.w = 0.9999;

int main(int argc, char** argv)
        ros::init(argc, argv, "od_transform");
        ros::NodeHandle n;
        robot_pose_broadcaster = n.createTimer(ros::Duration(.1), robotPoseCallBack);

//      tf::TransformBroadcaster aphabetagamma;

        return 0;

This code broadcast nothing. But when I uncomment the below line.

tf::TransformBroadcaster aphabetagamma;

This code publishes transform between map and base_link even though I never use variable aphabetagamma. Can someone help me understand this.


2016-12-13 04:09:35 -0500 received badge  Enthusiast
2016-10-17 10:21:00 -0500 asked a question Is kld_z in amcl parameters mapped with standard statistical z table?

Hi, In AMCL.cfg file the kld_z parameter has a range from 0 to 1 and the default value of 0.99. According to the paper on KLD sampling pg. 15 the probability 1-delta (the error between the true posterior and the sample based approximation is less than kld_err) has value 0.99. This information shows that the kld_z is a probabilty.

In pf.c of amcl this kld_z probabilty parameter is directly feed in the function named pf_resample_limit() as variable pf->pop_z. while the Paper on KLD sampling on page 13 suggest that this kld_z probability should be mapped with standard statistical z table. But i cannot find any such mapping in the code.