localizer

A clean and simple NDT localizer

This repo modified from Autoware lidar_localizer module. Unlike the module in Autoware with haveily dependency on a lot of packages(you need compile all the packages in Autoware project), this repo is clean, simple and with no dependencies. All you need is ROS, and a pcd file(the point cloud map).

Let's start our lidar-based localization learning with this simple repo!

Localization in a pointcloud map(pcd)

A demo video on MulRan dataset:

How to use

Build in your ros workspace

clone this repo in your ros workspace/src/, and then catkin_make (or catkin build):

cd catkin_ws/src/
git clone https://github.com/AbangLZU/ndt_localizer.git
cd ..
catkin_make

Get a pcd map

You need a point cloud map (pcd format) for localization. You can get a HD point cloud map from any HD map supplier, or you can make one yourself (of course, the accuracy will not be as high as the HD map).

make a point cloud by yourself, you can ref my blog: https://blog.csdn.net/AdamShan/article/details/106589633 (Chinese) and https://blog.csdn.net/AdamShan/article/details/106319382 (Chinese).

The code to produce a pcd map: https://github.com/AbangLZU/SC-LeGO-LOAM

Setup configuration

Config map loader

Move your map pcd file (.pcd) to the map folder inside this project (ndt_localizer/map), change the pcd_path in map_loader.launch to you pcd path, for example:

<arg name="pcd_path"  default="$(find ndt_localizer)/map/kaist02.pcd"/>

Config point cloud downsample

Config your Lidar point cloud topic in launch/points_downsample.launch:

<arg name="points_topic" default="/os1_points" />

If your Lidar data is sparse (like VLP-16), you need to config smaller leaf_size in launch/points_downsample.launch like 2.0. If your lidar point cloud is dense (VLP-32, Hesai Pander40P, HDL-64 ect.), keep leaf_size as 3.0。

Config static tf

There are two static transform in this project: base_link_to_localizer and world_to_map，replace the ouster with your lidar frame id if you are using a different lidar:

<node pkg="tf2_ros" type="static_transform_publisher" name="base_link_to_localizer" args="0 0 0 0 0 0 base_link ouster"/>

Config ndt localizer

You can config NDT params in ndt_localizer.launch. Tha main params of NDT algorithm is:

<arg name="trans_epsilon" default="0.05" doc="The maximum difference between two consecutive transformations in order to consider convergence" />
<arg name="step_size" default="0.1" doc="The newton line search maximum step length" />
<arg name="resolution" default="2.0" doc="The ND voxel grid resolution" />
<arg name="max_iterations" default="30.0" doc="The number of iterations required to calculate alignment" />
<arg name="converged_param_transform_probability" default="3.0" doc="" />

These default params work nice with 64 and 32 lidar.

Run the localizer

Once you get your pcd map and configuration ready, run the localizer with:

cd catkin_ws
source devel/setup.bash
roslaunch ndt_localizer ndt_localizer.launch

wait a few seconds for loading map, then you can see your pcd map in rviz like this:

give a init pose of current vehicle with 2D Pose Estimate in the rviz:

This operation will send a init pose to topic /initialpose.Then you will see the localization result:

The final localization msg will send to /ndt_pose topic:

---
header: 
  seq: 1867
  stamp: 
    secs: 1566536121
    nsecs: 251423898
  frame_id: "map"
pose: 
  position: 
    x: -94.8022766113
    y: 544.097351074
    z: 42.5747337341
  orientation: 
    x: 0.0243843578881
    y: 0.0533175268768
    z: -0.702325920272
    w: 0.709437048124
---

The localizer also publish a tf of base_link to map:

---
transforms: 
  - 
    header: 
      seq: 0
      stamp: 
        secs: 1566536121
        nsecs: 251423898
      frame_id: "map"
    child_frame_id: "base_link"
    transform: 
      translation: 
        x: -94.8022766113
        y: 544.097351074
        z: 42.5747337341
      rotation: 
        x: 0.0243843578881
        y: 0.0533175268768
        z: -0.702325920272
        w: 0.709437048124

Want to know more detail?

You can follow my blog series in CSDN (Chinese): https://blog.csdn.net/adamshan