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Point Cloud Rearrangement Function Introduction

Function Introduction

According to the position of the point cloud's horizontal angle and vertical angle, using preset horizontal angle range, vertical angle range, etc. to calculate the position of the point cloud, so that the position of the point cloud in the output array is consistent with the actual spatial position.

For example, according to the preset horizontal angle range (azi1 ~ azi2) and resolution (azi_resol), the point cloud width W is obtained. According to the preset vertical angle range (ele1 ~ ele2) and resolution (ele_resol), the point cloud height H is obtained. Then the size of the output array is W * H. If a point cloud has a horizontal angle of azi and a vertical angle of ele, then its offset in the output array is (azi - azi1) / azi_resol * H + (ele - ele1) / ele_resol.

Parameter Introduction

Configuration parameter definitions can be found in RemakeConfig

  • flag: Whether to enable rearrangement

  • min_azi / max_azi: Horizontal angle range

  • ring_azi_resolution: Horizontal angle resolution

  • max_azi_scan: Point cloud width, (max_azi - min_azi) / ring_azi_resolution, rounded to integer

  • min_elev / max_elev: Vertical angle range

  • ring_elev_resolution: Vertical angle resolution

  • max_elev_scan: Point cloud height, (max_elev - min_elev) / ring_elev_resolution, rounded to integer

Note: If parameters 2~8 maintain their original configuration, default parameters corresponding to the lidar model will be used

Additional References

Some lidars have non-uniform vertical angle resolution, meaning that in the case of one horizontal angle, there are some empty points in a column of point clouds (different vertical angle positions).

You can consider using channel numbers instead of vertical angles for rearrangement. The required modifications are as follows:

  1. In the DoRemake function in general_parser.cc, delete the calculation logic of elev_ and directly assign the input parameter elev to new_elev_iscan.

  2. Confirm the point cloud UDP version number of your lidar, which can be viewed through wireshark packet capture. Generally, the first two bytes in point cloud UDP packets are 0xEE 0xFF, and the following two bytes are the version number (converted to decimal). Using Pandar128E3X as an example, the version number is 1.4

  3. Navigate to file udp1_4_parser.cc, search for the DoRemake function, and modify the second input parameter elevation to channel number pointData.channel_index.