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Running NDT-MCL examples

Description: This tutorial goes through the steps to set up and run the ndt_mcl examples

Keywords: Localization, NDT-MCL

Tutorial Level: BEGINNER

Getting Started

For running the examples you need to have downloaded the complete perception-oru stack. Before compiling you should also install MRPT-GUI (used for the visualization). Instructions for installing it can be found from MRPT's home page.

Once that is complete and necessary ROS_PACKAGE_PATH is set, go to the ndt_mcl and compile

roscd ndt_mcl
rosmake

Next, download the necessary datasets:

cd data

./get_localization_data.sh
./get_mapping_data.sh

Now you should have mapping.bag and localization.bag in the ndt_mcl/data folder.

Running basic examples

There are two basic examples that can be executed:

roslaunch ndt_mcl 2d_ndt_mcl_node.launch
roslaunch ndt_mcl ndt_mcl_2d_offline.launch

Both of these use the localization.bag from the data folder and maps/ndt_0040.ndmap, which comes with the package. 2d_ndt_mcl_node.launch plays back the bag file and works as a node, while the offline version is an example for processing directly from the bag file.

Node subscribes to a sensor_msgs::LaserScan for input scans and uses tf tree to read the odometry. Please note that our implementation also expects that there is a "state topic", which is the ground truth information in our example files. When modifying the code for yourself, you should probably remove this.

Generating Map with fuser and localizing against it

First generate the map using the fuser. Start fuser:

roslaunch ndt_fuser fuser_2dlaser.launch

then on another terminal go to ndt_mcl/data, and start mapping set:

roscd ndt_mcl 
cd data

rosbag play mapping.bag

Once the mapping.bag is finalized, in terminal execute:

rosservice call /laser_fuser_2d/save_map "{}"

Now copy the saved map to ndt_mcl:

roscd ndt_fuser
cd maps
cp basement2d_map.jff ../../ndt_mcl/maps

Next change the name of the map in 2d_ndt_mcl_node.launch file to the basement2d_map.jff. Execute:

roslaunch ndt_mcl 2d_ndt_mcl_node.launch

Notes

The initial position in current version can be given through launch file or by having the ground truth information in the bag file (or system). In a near future there will be an option to set this from the rviz as well.