User's Manual
2 Absolute Time Calculation of Point Cloud Data Packet
In case of clock source from PTP, the user needs to connect a PTP master device to get the absolute time.
If PTP clock source is selected, LiDAR transmits only Point Cloud Data Packet with μs timestamps and 6 bytes UTC time. The μs timestamp
and UTC time in the Point Cloud Data Packet are used to calculate the packing time of this data packet.
The user can calculate the absolute time by the following method:
Retrieve the μs timestamp and the time information (UTC, decimal number) from the Point Cloud Data Packet. The absolute time of Point
Cloud Data Packet can be calculated by combining 2 parts: a) the 4 bytes μs timestamp; b) the 6 bytes UTC time information (decimal
number) in Point Cloud Data Packet.
1)
2)
3)
4)
NOTE
NOTE
The PTP master device is a third-party product and not included in LiDAR Package. The LiDAR clock just follow the PTP master device
by PTP protocol.
The timestamp and 6 bytes UTC time in Point Cloud Data Packet strictly follow the PTP time from PTP master device. There may have
offset with UTC time for certain PTP master device. Please verify the PTP master device configuration and calibration in order to get
precise UTC time from PTP master device.
The LiDAR works as PTP slave device and the PTP protocol is Plug&Play. No additional setup is required.
If PTP clock source is selected but no PTP master device available, the LiDAR will have an increasing time from invalid past time. If PTP
clock source was supplied and later stopped, the LiDAR will continue to count the time with internal clock.
The calculation of laser firing time remains the same whether PTP is used or not. Please refer to Appendix II for details.
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