User's Manual

Ethernet Header: 42 bytes

Table 3.5 GPS Data Packet Ethernet Header Definition

Ethernet II MAC 12 bytes

2 bytes

20 bytes

4 bytes

Destination: Broadcast (0xFF: 0xFF: 0xFF: 0xFF: 0xFF: 0xFF), Source: (xx:xx:xx:xx:xx:xx)

0x08, 0x00

Version, Header Length, Diﬀerentiated Services, Field, Total Length, Identiﬁcation, Flags, Fragment

Oﬀset, Time to Live, Protocol, Header Checksum, Source IP Address, Destination IP Address

UDP source port (0x2710, represents10000), destination port (0x277E, represents 10110)

Length 2 bytes (0x208, represents 520 bytes), checksum 2 bytes

Ethernet Data Packet Type

Internet Protocol

UDP Port Number

UDP Length and Checksum

3.2.1 GPS Data Packet – Ethernet Header

Each GPS Data Packet has a 42 bytes Ethernet Header and 512 bytes UDP Data. All the multi-byte values are the unsigned type and in Little

Endian format. GPS UDP Data Packet will be triggered every second, and the port is 10110.

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Before receiving the GPS module data, the rising edge of the internal 1Hz signal of the LiDAR will trigger a GPS Data Packet. The initial GPS

time data in the packet will be counted from 000101000000 (yymmddhhmmss, year, month, day, hour, minute, second) and this unreal GPS

time can also increase according to internal 1Hz signal of LiDAR as long as GPRMC information is not available at the beginning. If LiDAR

receives PPS signal and GPRMC data from GPS module, the local 1Hz signal of the LiDAR will be locked to the PPS signal. GPS Data Packet

is still triggered by the rising edge of the internal 1Hz signal. Meantime, the GPS time data in the Packet will be reset to actual GPS time by

GRPMC information from GPS module.

GPS module sends ﬁrstly the PPS signal, then the GPRMC information. The LiDAR can extract the UTC information and stamp 6 bytes UTC

time (Year:Month:Day:Hour:Minute:Second) into Point Cloud UDP Packet. User can then add 4 bytes timestamp and 6 bytes UTC time in

Point Cloud UDP to achieve absolute time for the UDP packet.

As long as the GPS signal is available, the GPS time in the packet will update according incoming GPRMC information. If GPS module stops

sending data, LiDAR will still trigger a GPS Data Packet following the internal 1Hz signal and GPS time data in the Packet will be counted on

the base of previously actual GPS time.

3.2 GPS Data Packet Ethernet Header/UDP Data

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