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Data Collection for Lidar-Radar calibration
RADAR - LIDAR Calibration Data Collection Documentation
Calibration Target:
Our current method for radar-lidar calibration uses a plane wooden board along with a trihedral corner reflector as the calibration target.
The trihedral corner reflector is made by combining three triangles at an angle of 90 degrees. It has a high radar cross-section, and it is easily distinguishable from other objects. The side length can be chosen of any length, higher values will have higher radar cross-sections. For internal testing purposes, we used the trihedral corner reflectors made of aluminium.
Please note that:
- 1.The plane wooden board can be of any size.
- 2.The trihedral corner reflector can be of any length.
The trihedral corner reflector is taped to the back of the plane wooden board, as shown in the image below.
Note: The tip of the trihedral corner reflector must be in line with the centroid of the plane board.
Data for Radar-Lidar calibration:
The following are some important points to be noted while collecting the data:
- 1.Place the board at roughly 2m - 3m from the lidar and radar. The readings from radar will be more accurate when the corner reflector is placed at a closer position, and the accuracy decreases as we move farther away from the radar. But in case of Lidar, the board needs to be placed at a farther position to get the best coverage of the board.
- 2.So we need to be very careful while placing the board in radar and lidar fields of view. We must make sure that the lidar point captures the complete board by not placing it farther away from the sensors.
- 3.Most of the radars available in market has significantly very less field of view in terms of azimuth (angle in horizontal direction) and elevation (angle in vertical direction), so please make sure to place the tip of corner reflector very close to the line of sight of the radar to get accurate results.
Place the board in front of both the sensors, making sure that the above points are taken into consideration. The target and all the sensors should be static while collecting the data. In order to avoid time synchronization problems, please keep the board and the sensors stationary for at least 10 seconds while collecting each set of calibration data.
Fix a position of the board and collect the data in both radar and lidar and save them, preferably with the same name. Repeat the process for at least 5-6 times changing the position of the board and save all the data from both sensors.