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Mapora Rosbag

Mapora Rosbag is an open-source georeferenced point cloud generating tool. Basic idea is putting each individual point cloud onto the pose which are in the same line in the rosbag database.

One of the important point for exporting tightly coupled point clouds with Mapora Rosbag is having high accurate GNSS/INS positions. To provide that, it is highly recommended to use RTK corrections while data collection.

The other important issue is having precise LiDAR-IMU calibration angles. If not, the possibility of having bad features in map is very high.

Some of the views of the point clouds can be seen below.

mapora_building mapora_cars mapora_environment

Data Collection Procedure

For data collection, A LiDAR and a GNSS/INS sensor which supports ROS2 is needed. The system works with rosbags and the data of the sensors are needed to be collected as rosbag in the same time.

Basically, the data can be collected with a Mobile Mapping System (MMS). A sensor setup is needed for this procedure. With the system, fixed position sensors are provided. A computer is able to collect rosbag is needed. After being sure all the data comes to the computer correctly, the rosbag can be started to record.

mapora_setup1 mapora_setup2

System Requirements

  • PC which runs Ubuntu 22.04 (Ubuntu version must be at least 20.04)

    • Mapora Rosbag is tested on Ubuntu 22.04 with ROS2 Humble.

  • A LiDAR which supports ROS2

    • One of the needed data are the point cloud comes from the LiDAR sensor. Mapora Rosbag works in ROS2. So, point clouds needed to be collected as a rosbag.

  • A GNSS/INS which supports ROS2

    • The other needed data is GNSS position. It is highly recommended to use RTK corrections due to the need to increase of the accuracies of the GNSS/INS positions.

Installation & Build

Installation and building procedure is the same of the Mapora. You can find the instructions here.

Input Files

Input Description
Collected Rosbag Files A rosbag file which includes GNSS/INS and LiDAR topics.

Output Files

Output Description
Point Clouds Georeferenced .las formatted point cloud files.

Run the Mapora Rosbag

To running the Mapora Rosbag only a rosbag file is needed as input file. After filling the /params/mapora_rosbag_params.yaml the tool is ready to run.

WARNING:

Please be aware that to use the point cloud distortion corrector in Mapora Rosbag, the point cloud data need to have a timestamp field. If not, please make the correct_distortions: false in mapora_params.yaml.

After building, at the environment directory:

source install/setup.bash

ros2 launch mapora mapora_rosbag.launch.py

Example Data

To see how Mapora Rosbag works, an example data directory is provided. This link contains the example data of the Mapora Rosbag. The example data needs to be in the example_data/mapora_rosbag/ directory in the package. In params/mapora_rosbag_params.yaml file, the params are set to run the example data. You can observe the file paths in this file. After you put all data files into right directory which is example_data/mapora_rosbag/, .las exports of the Mapora Rosbag would be in the example_data/mapora_rosbag/output_las/ directory.

Params

Param Description
project_namespace What is the name of this project for the point clouds that will be exported.
las_export_directory Export directory of the point clouds.
save_point_cloud_after_msgs Save point cloud after every (n) msgs.
r_x LiDAR-IMU calibration roll angle (angle around X-axis).
r_y LiDAR-IMU calibration pitch angle (angle around y-axis).
r_z LiDAR-IMU calibration yaw angle (angle around z-axis).
t_x LiDAR-IMU calibration X distance.
t_y LiDAR-IMU calibration Y distance.
t_z LiDAR-IMU calibration Z distance.
max_point_distance_from_lidar What is the maximum distance of LiDAR points for mapping?
min_point_distance_from_lidar What is the minimum distance of LiDAR points for mapping?
err_pos_x Filter the GNSS/INS frames which have more than X error.
err_pos_y Filter the GNSS/INS frames which have more than Y error.
err_pos_z Filter the GNSS/INS frames which have more than Z error.
err_rot_x Filter the GNSS/INS frames which have more than roll error.
err_rot_y Filter the GNSS/INS frames which have more than pitch error.
err_rot_z Filter the GNSS/INS frames which have more than yaw error.
correct_distortions Enable or disable point cloud distortion corrector.
base_link_tf_name Name of the base link TF for point cloud distortion corrector.
lidar_tf_name Name of the LiDAR TF for point cloud distortion corrector.
point_cloud_timestamp_field The name of the timestamp field in the point cloud data.
rosbag_path System path of the rosbag directory.
point_cloud_topic Name of the PointCloud2 topic.
gnss_topic Name of the NavSatFix topic.
imu_topic Name of the Imu topic.
twist_with_covariance_stamped_topic Name of the TwistWithCovarianceStamped Topic.