User's Manual

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Appendix II Absolute Time and Laser Firing Time
II.1 Absolute Time of Point Cloud Data Packets
For Pandar128, there are 2 blocks of ranging datain theBody ofeach Point Cloud Data Packet, as shown below. Each block contains the ranging data from
128 channels, one return per channel.
Point Cloud Data Packet – Body: 772 bytes (2 blocks)
Block 1
Block 2
Azimuth 1
Azimuth 2
Channel 1
Channel 1
Channel 2
Channel 2
…
…
Channel 128
Channel 128
◼ Single Return Mode
The ranging data generated by one round of firing is stored in one block.
The absolute time of a Point Cloud Data Packet is the time when the LiDAR sends a command to trigger a round of firing that will be stored in Block 2.
◼ Dual Return Mode
The ranging data generated by one round of firing is stored in the two blocks of one packet
▪ Block 1 is the last return, and Block 2 is the strongest return
▪
If the last and strongest returns coincide, the second strongest return will be placed in Block 2
▪
The start time of Block1 and Block 2 is the same
Theabsolutetime of a Point Cloud Data Packet is thetime when the LiDAR sends a commandto triggera roundof firing that will be stored in Blocks1 & 2.