Synchronizing With A Gps Receiver - MikroTik RouterOS v2.9 Reference Manual

• Precise Positioning Service (PPS) that is used only by U. S. and Allied military, certain U. S.
Government agencies, and selected civil users specifically approved by the U. S. Government.
Its accuracy is 22m horizontally, 27.7m vertically and 200ns of time
• Standard Positioning Service (SPS) can be used by civil users worldwide without charge or
restrictions except that SPS accuracy is intentionally degradated to 100m horizontally, 156m
vertically and 340ns of time
GPS system is based on 24 satellites rotating on 6 different orbital planes with 12h orbital period. It
makes that at least 5, but usually 6 or more satellites are visible at any time anywhere on the Earth.
GPS receiver calculates more or less precise position (latitude, longitude and altitude) and time
based on signals received from 4 satellites (three are used to determine position and fourth is used
to correct time), which are broadcasting their current positions and UTC time.
MikroTik RouterOS can communicate with many GPS receivers which are able to send the
positioning and time via asynchronous serial line using NMEA 0183, NMEA/RTCM or Simple
Text Output Protocol. Note that you might need to configure the router's serial port in order to work
with your device. For example, many GPS receivers work on 4800bit/s bitrate, to the same should
be set in the /port menu for the respective serial port.
Precise time is mainly intended to be used by built-in NTP server, which can use it as a time source
without any additional configuration if GPS is configured to set system time.
Additional Documents
• Global Positioning System - How it Works

Synchronizing with a GPS Receiver

Home menu level: /system gps
Property Description
enabled ( yes | no ) - whether the router will communicate with a GPS receiver or not
port ( name ) - the port that will be used to communicate with a GPS receiver
set-system-time ( time ) - whether to set the system time to the value received from a GPS receiver
or not
Notes
If you are synchronizing system time with a GPS device, you should correctly choose time zone if it
is different from GMT as satellites are broadcasting GMT (a.k.a. UTC) time.
Example
To enable GPS communication through serial0 port:
[admin@MikroTik] system gps> print
enabled: no
port: (unknown)
set-system-time: yes
[admin@MikroTik] system gps> set enabled=yes port=serial0
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