Create a map of the lab with the robot Pioneer and SICK LMS:2

Yesterday I made a map of the laboratory using data from the laser recorded into a bag file and running slam_gmapping node.

I found a very simple mistake in my tf_listener.cpp code and searching through the sscrovers svn I found the same one. It is approximately at line 20 and it concerns the transformation of the new point created.

The original file displays the following:

try{ geometry_msgs::PointStamped base_point;
listener.transformPoint("base_laser_link", laser_point, base_point);

The transformation is in fact supposed to be from base_laser_link frame to base_link frame. And that is why base_point is created, to store the same information as laser_point (of base_laser_link frame) but now in the desired frame that should be base_link. The result is the following:

try{ geometry_msgs::PointStamped base_point;
listener.transformPoint("base_link", laser_point, base_point);

I then ran all of the nodes in exactly the same way I had been doing it and this time a map.pgm and a map.yaml file were created.

The only difference in my procedure was that, exactly at the time I was going to play the bag file, I pushed the reset button on rviz. In spite of this, gmapping still displays the TF_OLD_DATA error. I have been reading about it and several users in the mailing list argue that they had dealt with this same problem, both when running gmapping and other nodes.

Building a map using logged data

Based on one of the gmapping tutorials:

http://www.ros.org/wiki/slam_gmapping/Tutorials/MappingFromLoggedData#download

1. Run a core

$ roscore

2. Set use_sim_time param to true

$ rosparam set use_sim_time true

3. Run the slam_gmapping node that will take scans on the base_scan topic

$ rosrun gmapping slam_gmapping scan:=base_scan

4. Play a bag file, in this case I played the example available

$ wget http://pr.willowgarage.com/data/gmapping/basic_localization_stage.bag
$ rosbag play basic_localization_stage.bag

5. In order to watch the mapping process I ran nav_view

$ rosrun nav_view nav_view /static_map:=/dynamic_map

 6. Save map  $ rosrun map_server map_saver  [ INFO] 0.000000000: Writing map occupancy data to map.pgm [ INFO] 0.000000000: Writing map occupancy data to map.yaml [ INFO] 0.000000000: Done

This is how the publications and subscriptions of topics looks like: