LeiShen Intelligent System LiDAR C128 Series, Инструкция по эксплуатации, Страница: 79 / 89

LeiShen Intelligent System CO., LTD.
LeiShen Intelligent System CO., LTD.
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5.4 External time synchronization
The synchronization of the laser radar with the external system is realized through:
1. When synchronized with GPS timing system, GPS will be lock, and the radar counts in microseconds from zero when it receives PPS
from timing system. According to UTC provided by Global Positioning System and the radar counting time, calculate the time when packet is
obtained, see 4.1 below for details;
2. When the external system provides synchronization signal (1 second per cycle), the radar counts from microseconds in microseconds
when receiving the external synchronous rising edge signal pulse provided by the external system, and the count value is assigned to the main
data stream time. The count value is assigned to the byte bit output of the main data stream timestamp. When the external synchronous rising
edge signal arrives, it will be cleared and recounted, see 4.2 for details;
3. When the radar starts without GPS signal and no external synchronization signal is connected, it runs on its own internal clock, counting
in microseconds and the count value is assigned to the byte of the main data stream timestamp, count to 1 hour and restart, see 4.3 for details.
Four byte timestamp is a 32-bit unsigned integer, this value represents the reception time of the last data point of a packet, and it’s arranged
in Little Endian mode. The 16-channel laser is transmitted once every 50us (20K transmission repetitive frequency) at the interval of 3.125 us.
Each data packet has 24 16-channel laser data sets, a total of 192 laser pulse triggers, as referred to in 1.1, two data sets store the primary and
secondary echoes generated by 16 laser receiving pulses at a time, and the data accumulation for entire data packet takes 0.6 ms. This means that
the data rate is 1666.7 packets per second (1/0.6ms). GPS timestamp feature is used to determine the launch time of laser. This allows the user to
match the data points of the Leishen C16 Lidar to the pitch, roll, yaw, latitude, longitude and altitude of GPS/Inertial Measurement System.