MOTOTRBO GPS in a nutshell

Radios with model names ending with a 1 (e.g. DP3601 or DM4401) have an integrated GPS receiver. This receiver is purely a reporting tool (i.e. the radio user cannot see where they are like on a traditional GPS unit). MOTOTRBO radios uses a protocol called LRRP (Location Request Response Protocol) to send GPS updates to a predefined Radio ID (i.e. destination address). LRRP uses triggers to schedule GPS updates: these include GPIO event; delta time; delta distance or immediate.

GPS updates are processed by a location server (effectively a standard PC with a tracking application on it). The operator (person) sends a location request to a radio via the tracking application installed on the PC. The server is connected to a Control Station, which is used to send the request. This location request contains information about the triggers: for example, send GPS data every ten minutes or every 1 kilometer, whichever happens first (this is chosen by the operator via the location application).

The Control Station can be any MOTOTRBO radio - mobile or portable. The radio is connected to the server via a standard USB cable. This radio would be programmed to monitor the radio channel or system.

[Edit 10.09.13] Note that as of system release 2.2, control stations are not required and certain Application Partner products are able to access the radio network directly via the repeaters. This uses the NAI feature (Network Application Interface).

The radio stores this location request and when one of the triggers have been reached, the radio sends a GPS packet (takes less than 600ms). The GPS is sent as UDP/IP data over the air, to the predefined Radio ID. The radio which receives this packet forwards this to the PC, which displays the radio location on a map. There are different ways to handle the GPS update, in terms of channels and coordination.

Another MOTOTRBO feature which works hand-in-hand with GPS is ARS (Automatic Registration Service). This causes the radio to send a registration packet every time the user switches on or (optionaly) changes site. ARS is also supported in non-GPS models.

The map and location request management, is part of one of many possible applications from several possible Motorola Application Partners.

More details on how GPS is handled in MOTOTRBO can be found in the MOTOTRBO System Planner. More information on which Motorola Application Partners produce GPS tracking applications can be found in the Application Partner Catalogue. Both of these documents are available to Channel Partners, for download from Motorola Online. The Application Partner catalogue is available for download on my Blog or on Motorola's website.

If you dont have access to Motorola Online, you can request a copy of the latest MOTOTRBO System Planner from your Motorola Supplier. A summarised version of the MOTOTRBO Application Partner Catalogue is available on the web at


  1. Hi Wayne!
    I discovered that in my conditions (DP3601 radio placed at a window of house) the accuracy of GPS data is very poor. Constant error is about 50m and sometimes I observed surges of GPS marks on distance of 300m. Could you tell me is this normal for Motorola radios and what are the reasons of such problem?

    1. What you are seeing is quite normal for *all* GPS receivers. The most likely reason for the error you are seeing is the fact that the radio was switched on then placed next to a window with no clear view of the sky. Try powering up the radio outside with a full view of the sky and leave it for about 2-3 minutes before putting it next to the window.

      You are also possibly comparing the performance with a car navigation system (e.g. TomTom; Garmin et al.) - these devices use snap to roadway which places the car icon on the nearest road giving the appearance of excellent accuracy.

      Chapter 2.4.1 of this publication is also worth reading.

    2. Thank you Wayne.
      And one more question is what does it mean "The radio stores this location request and when one of the triggers have been reached, the radio sends a GPS packet"? I've never heard about GPS triggers in Mototrbo radios. Does this mean that control station sends GPS request only once till radio is registered and this one sends its own position information by itself in defined intervals of time without requests?

    3. Correct, the server (control station) only needs to send a single request containing the trigger information (time or distance or both). The server could optionally only do this once the radio has powered up and registered (ARS).

      Optionally, the dispatch operator could request an immediate update in which case the radio would respond as soon as possible with coordinates - even if the time/distance limit hasn't been reached.

  2. Does using GPS on MotoTRBO radios require specific antennas? in case of portable radios i heard normal antennas are acting as gps antennas too, but i'm not sure if mobile radios are fine with their own antennas? are they require one antenna for sending radio waves and one for receiving gps signals? or maybe they have built in gps signals like gps devices?

    1. On the DP3000 series the GPS antenna was part of the radio antenna so a special antenna was required.
      On the DP4000 series (incl. DP3441) the GPS antenna is in the radio.

      On all MOTOTRBO mobiles however you need a separate GPS antenna and coax cable.

    2. once again you were helpful and yet very fast. you simply are the best. Thanks

  3. Hello,

    I have a question about GPS system. In my situation, I have DM 3601 with GPS in my car and i have DM 4600 like control station on my PC with application.

    But I notice that it is the DM3601 in my vehicle that sends its GPS data about 15 -20 secondes) to the control station, not the other way around. Is this normal ?

    Is not the DM4600 base to ask for the GPS position of mobile radios ?



    1. What you are seeing is normal. The base will only need to send one request to get continious updates.

    2. Hello,

      Thank you.


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