The method makes use of the property that pointclouds from lidars appear more 'crisp' when the calibration is correct. The system attempts to find the transform between a lidar and the given poses such that the distance between any two lidar points in the resulting fused pointcloud is minimized. Poses can be provided as a TransformStamped message or in Maplab's CSV format
This library is pretty new and only tested on a couple of datasets, so expect some issues when you first run it.
For most systems the node can be run without tuning the parameters. By default two optimizations are performed, a rough global optimzation followed by a local refinement.
| Column | Description |
|---|---|
| 1 | timestamp ns |
| 2 | vertex index (not used) |
| 3 | position x |
| 4 | position y |
| 5 | position z |
| 6 | orientation quaternion w |
| 7 | orientation quaternion x |
| 8 | orientation quaternion y |
| 9 | orientation quaternion z |
Note that Maplab has two CSV exporters. This file-format is the same as produced by exportPosesVelocitiesAndBiasesToCsv but differs from the output of exportVerticesAndTracksToCsv
This package depends on ROS, PCL and ncurses. Ncurses can be installed with sudo apt install libncurses5-dev
| Parameter | Description | Default |
|---|---|---|
min_point_distance |
Minimum range a point can be from the lidar and still be included in the optimization. | 0.0 |
max_point_distance |
Maximum range a point can be from the lidar and still be included in the optimization. | 100.0 |
keep_points_ratio |
Ratio of points to use in the optimization (runtimes increase drastically as this is increased). | 0.01 |
min_return_intensity |
The minimum return intensity a point requires to be considered valid. | -1.0 |
motion_compensation |
If the movement of the lidar during a scan should be compensated for. | true |
estimate_point_times |
Uses the angle of the points in combination with lidar_rpm and clockwise_lidar to estimate the time a point was taken at. |
false |
lidar_rpm |
Spin rate of the lidar in rpm, only used with estimate_point_times. |
600 |
clockwise_lidar |
True if the lidar spins clockwise, false for anti-clockwise, only used with estimate_point_times. |
false |
| Parameter | Description | Default |
|---|---|---|
use_n_scans |
Optimization will only be run on the first n scans of the dataset. | 2147483647 |
input_bag_path |
Path of rosbag containing sensor_msgs::PointCloud2 messages from the lidar. | N/A |
transforms_from_csv |
True to load scans from a csv file, false to load from the rosbag. | false |
input_csv_path |
Path of csv generated by Maplab, giving poses of the system to calibrate to. | N/A |
output_pointcloud_path |
If set, a fused pointcloud will be saved to this path as a ply when the calibartion finishes. | "" |
output_calibration_path |
If set, a text document giving the final transform will be saved to this path when the calibration finishes. | "" |
| Parameter | Description | Default |
|---|---|---|
local |
If False a global optimzation will be performed and the result of this will be used in place of the inital_guess parameter. |
false |
inital_guess |
Inital guess to the calibration (x, y, z, rotation vector, time offset), only used if running in local mode. |
[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0] |
max_baseline |
Maximum distance between sensors to consider during the global optimization stage. | 1.0 |
max_time_offset |
Maximum time offset between sensor clocks in seconds. | 0.1 |
angular_range |
Search range in radians around the inital_guess during the local optimization stage. |
0.5 |
translational_range |
Search range around the inital_guess during the local optimization stage. |
0.25 |
max_evals |
Maximum number of function evaluations to run | 2000 |
xtol |
Tolerance of final solution | 0.000001 |
knn_batch_size |
Number of points to send to each thread when finding nearest points | 1000 |
knn_k |
Number of neighbours to consider in error function | 1 |
global_knn_max_dist |
Error between points is limited to this value during global optimization. | 1.0 |
local_knn_max_dist |
Error between points is limited to this value during local optimization. | 0.1 |
time_cal |
True to perform time offset calibration | true |