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Appendix I Absolute Time and Laser Firing Time

I.1 Absolute Time of Point Cloud Data Packets

The absolute packing time of a Point Cloud Data Packet is the sum of date, time (accurate to the second) and μs time.

▪ Date and Time can be retrieved either from the current Point Cloud Data Packet (6 bytes, year, month, date, hour, minute, second), or from the previous

GPS Data Packet (6 bytes of Date and 6 bytes of Time).

▪ μs time can be retrieved from the current Point Cloud Data Packet (4 bytes of Timestamp)

NOTE The calculation of absolute time is different when PTP protocol is used. See Appendix II PTP Protocol.

I.2 Laser Firing Time

I.2.1 Start Time of Each Block

Assuming that the absolute packing time of a Point Cloud Data Packet is t0 (detailed in I.1), the start time of each block (the time when the first laser starts

firing) can be calculated.

For PandarQT, there are 4 blocks of ranging data in the Body of each Point Cloud Data Packet, as shown below. Each block contains the ranging data from

64 channels, one return per channel.

Point Cloud Data Packet – Body: 1032 bytes (4 blocks)

Block 1

Block 2

Block 3

Block 4

Azimuth 1

Azimuth 2

Azimuth 3

Azimuth 4

Channel 1

Channel 2

…

Channel 64