structure of the GPRMC sentence is as follows:
$GPRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>*hh
<1> UTC Time
<2> Receiver status, A=active, V=void
<3> Latitude
<4> Latitudinal hemisphere N (northern hemisphere) or S (southern hemisphere)
<5> Longitude
<6> Longitudinal hemisphere E (east longitude) or W (west longitude)
<7> Speed over the ground(knots)
<8> Track made good (degrees True)
<9> UTC date
<10> Magnetic declination
<11> Magnetic declination direction, E (east) or W (west)
<12> Mode indicator (A=autonomous, D=differential, E=estimated, N=not valid)
* The last hh is the XOR sum of all characters from $ to *
Note:
1. The sending time interval of 1 PPS pulse needs to be controlled within 1s±100us;
2. The status bit in the GPRMC message must be A valid before time synchronization is allowed;
3. The length of GPRMC messages sent by existing GPS modules on the market is not consistent.
The length of GPRMC messages reserved in the DIFOP packet of RS-Helios-1615 is up to 86 bytes,
which is compatible with the GPRMC message format sent by most GPS modules on the market. If
an incompatibility occurs, please contact RoboSense technical support.
5.6.3 PTP Time Synchronization
PTP (Precision Time Protocol) is a time synchronization protocol, which itself is only used for high-
precision time synchronization between devices, but it can also be borrowed for frequency
synchronization between devices. Compared with various existing time synchronization
mechanisms, PTP has the following advantages:
1) Compared with NTP (Network Time Protocol, Network Time Protocol), PTP can meet higher-
precision time synchronization requirements. NTP can generally only achieve sub-second time
synchronization accuracy, while PTP can reach sub-microsecond time synchronization accuracy.
2) Compared with GPS (Global Positioning System), PTP has lower construction and maintenance
costs.
5.6.4 PTP wiring Method
To use the PTP synchronization method, you need to make the following preparations, and then
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