GPS

Document revision 1.1 (25-Jul-2003)
This document applies to MikroTik RouterOS v2.7

Table of Contents
Summary
Specifications
Related Documents
Description
Synchronizing with a GPS Receiver
Monitoring GPS
Additional Resources

Summary

Global Positioning System (GPS) receiver can be used by MikroTik RouterOS to get the precise location and time (which may be used as NTP time source)

Specifications

Packages required : gps
License required : Any
Home menu level : /system gps
Standards and Technologies : GPS, NMEA 0183, Simple Text Output Protocol
Hardware usage: not significant

Description

Global Positioning System (GPS) is used for determining precise location of a GPS receiver. There are two types of GPS service:

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.

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.

Synchronizing with a GPS Receiver

Submenu level : /system gps

[admin@MikroTik] system gps> print
            enabled: no
               port: (unknown)
    set-system-time: yes
[admin@MikroTik] system gps>

Property Description

enabled (yes | no) - whether router will communicate with a GPS receiver
port (name) - the port will be used to communicate with a GPS receiver
set-system-time - whether to set the system time to what received from a GPS receiver

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
[admin@MikroTik] system gps> print
            enabled: yes
               port: serial0
    set-system-time: yes
[admin@MikroTik] system gps>

Monitoring GPS

Command name: /system gps monitor

Description

This command is used for monitoring the data received from a GPS receiver

Property Description

date-and-time (read-only: text) - data and time received from a GPS receiver
longitude (read-only: text) - longitude of the current location
latitude (read-only: text) - latitude of the current location
altitude (read-only: text) - altitude of the current location
speed (read-only: text) - mean velocity
valid (read-only: yes | no) - whether the showings are actually valid (e.g. you can set a GPS receiver to the demo mode to test the connection, in which case you will receive information, but it will not be valid)

Examples

[admin@MikroTik] system gps> monitor
    date-and-time: jul/23/2003 12:25:00
        longitude: "E 24 8' 17''"
         latitude: "N 56 59' 22''"
         altitude: "-127.406400m"
            speed: "0.001600 km/h"
            valid: yes

[admin@MikroTik] system gps>

Additional Resources

For additional information on how GPS works see:

Global Positioning System - How it Works