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Using Team Tracker with NMEA/APRS (Generic) Tracking Devices

Additional GPS Information


The Team Tracker in Terrain Navigator Pro provides valuable safety information for search and rescue teams, firefighters or anyone else who needs to know where workers are in the field at all times.

In order to use the team tracker feature, use the TNP Mobile App for Internet-based connectivity and tracking of teams. Alternatively, your computer could be hooked up to a 2-way radio transceiver. The locations of those who carry the compatible equipment are automatically tracked and plotted on Terrain Navigator Pro’s maps in real time. Workers can also transmit waypoints and send text messages to one another.

While the Team Tracker module provides "plug and play" compatibility with the TNP Mobile App and certain hardware vendors (including Pryme radio, and Infinity Gear), there is also an additional level of compatibility through support of generic NMEA sentences that can be interfaced with certain APRS systems. This technical document gives the details on how to set up such a configuration.

Special Note

As indicated above, use of the NMEA interface with the APRS system is not a "plug and play" solution. Various hardware and software products must be obtained and configured in order for this to work as expected. Trimble can not make specific recommendations on which hardware is best suited for your organization. Moreover, because of the wide variety of products available, it is impossible for Trimble to provide extensive support during the configuration process.

Instead, we provide this technical document (which includes a list of user-suggested hardware) to aid in the setup and configuration process. The configurations listed here were not tested specifically by our staff, but rather by volunteers who have successfully used the Team Tracker module in their set ups. We welcome additions and corrections to this list.

Compatible Hardware (as reported by Team Tracker customers)

1. Kenwood TM-D700a Full Dual Bander 144/440MHz Radio.
• Use a cable from the GPS port on the radio to the serial port on the computer.
• Enabled APRS Waypoint output in the Radio Menu. (Menu 3-3 set to 9 Digit NMEA).
• In TNP GPS Setup, specify NMEA Tracker, Track using WPL messages.
• There is no filtering using this method. Any APRS station heard by the radio will get sent to TNP and displayed on the map.

2. DR-135 MkIII Monoband Mobile/Base
• Microtrack AIO as the GPS transmitter: (Callsign: BGSAR-4, Digi: WIDE 1-1, Freq: 144.390, Text: KJ4PBJ, send every: 4)
• Check boxes: send altitude, send NMEA, time stamp HMS.
• Enable time slotting if more than one AIO transmitting with offset time.
• Make sure baud rate is set at 4800 bps inside Alinco (this is the default setting).
• Out of Alinco radio, if using a serial to USB adaptor, make sure latest driver installed, and set at 4800 bps to computer. (Avoid using a low-quality USB to Serial adaptor, including those sold at "Radio Shack".)
• If any reprogramming of AIO, radio or TNP is done, make sure to power down everything and restart. Sometimes reprogramming of a particular unit is held in a buffer.

3. KPC-3+ Packet Communicator
• Used with a variety of public safety portable radios equipped with uBlox LEA-5H OEM GPS receiver modules using Sarantel quad helix antennas.
• Radios are configured, programmed and jumpered to allow timed and polled location update.
• Interfaced with a Byonics TinyTrak3+ surface mount APRS encoder board (as the unit controller)
• Controlled via a custom-programmed interface board that takes the data from the ARS format and constructs the WPT message. The interface board unit also has the controls that allow individual or group polling.
• This system operates in a separate band from the team's voice radios to prevent desensitization of their voice receivers in the field or general interference at a system level.

4. OpenTracker+ (OT1+)
• Used to decode standard APRS packets generated by a Byonics TinyTrak3+ surface mount APRS encoder.
• Preliminary compatibility with TNP established. Further testing is needed.

Connecting Terrain Navigator Pro's Team Tracker Module

After setting your hardware to transmit NMEA sentences, follow these instructions:
1. Connect the appropriate hardware to a Serial Port (either real or virtual) on your computer. Consult your hardware manufacturer for assistance, if needed, ensuring that NMEA sentences are being transmitted to that port.

2. Start Terrain Navigator Pro.

3. Open the GPS menu and choose Setup to establish the initial communication settings for the radio transceiver. Set the Manufacturer to NMEA - generic and the Unit to NMEA Tracker. Specify the Port - matching the COM Port connected in step 1. Press Port Settings to adjust the Baud Rate, if needed. Finally, choose the desired tracking mode by pressing Advanced. (See below for additional information regarding the tracking mode.) Once these settings are established, it is not needed to repeat this step (unless you wish to use Terrain Navigator Pro in conjunction with a different GPS unit.)

4. Open the GPS menu and select Connect. Once your computer has established communication with the transceiver, it is ready to receive locations and messages from the handheld units in the field.

5. Once Terrain Navigator Pro begins to receive properly formatted NMEA sentences, their positions will appear on the maps.

6. The next time Terrain Navigator Pro is started, open the GPS menu and choose Connect to establish the link between the NMEA compatible hardware and Terrain Navigator Pro. (You do not need adjust the GPS Setup unless you have connected a different handheld GPS to your computer, or made changes to your hardware configuration.)

7. Once Terrain Navigator Pro is connected to the hardware, any positions, waypoints, and text messages will automatically appear. Do not select the 'Tracking' option from the GPS menu unless you wish to track the position of the base GPS unit while also tracking the position of other radios. (This may be useful while the base station is in a traveling mobile unit.)

Note that it is not possible to transmit or receive routes or tracks from a NMEA tracking GPS. However, waypoints can be received (in the WPL string) when tracking using TLL messages. TXT can also be used to receive a text message from the remote GPS.

Receiving NMEA Transmissions and Plotting Remote Positions

To start receiving these transmissions, choose 'Connect' from the GPS menu in Terrain Navigator Pro. The screen will automatically update with the positions of the field units as soon as their next transmission is received. If it is desired to track the position of the base station (as in a mobile command center) then you may also use the options found under the GPS Tracking menu item. (Note that these options have no affect on any remote GPS positions.)

Setting the Tracking Mode - Specifying NMEA Sentence Interpretation

The Advanced button in the GPS Setup window is used to specify which NMEA sentences trigger the display of remote positions. 'Track using WPL messages' allows a remote position to be plotted through the use of the NMEA WPL sentence. 'Track using TLL messages' allows a remote position to be plotted through the use of the NMEA TLL sentence. Specify the desired mode by pressing the Advanced button in the GPS Setup window.

Track Using WPL Messages
When tracking using WPL messages, the NMEA tracking module responds to the standard NMEA WPL string with a format of:
which is interpreted as:
WPL - Location of remote position (WayPoint Location)
4305.5751,N - Latitude (formatted as: DDMM.mmmm)
07146.5827,W - Longitude (formatted as: DDDMM.mmmm)
WAYPT1 - Waypoint Name
*2B - Checksum data; Note: always begins with *

If a common waypoint name (WAYPT1 in the above example) is used, the positions will be traced together to show a route over time. Otherwise, it will be assumed that the waypoints received represent separate remote GPS units, and will be plotted as such.

Note: Even when 'Track using WPL messages' is selected, TLL sentences (described below) will also be recognized.

Track Using TLL Messages
When tracking using TLL messages, the NMEA tracking module responds to the standard NMEA TLL string with a format of:
which is interpreted as:
TLL - Location of remote position (Target Latitude Longitude)
01 - Target Number (not used/ignored)
4305.4281,N - Latitude (formatted as: DDMM.mmmm)
07147.3170,W - Longitude (formatted as: DDDMM.mmmm)
TARG1 - Target Name 123456.21 - Target Time (not used/ignored)
T - Target Status (S - SOS need help, otherwise ignored)
R - Reference target (not used/ignored)
*57 - Checksum data; Note: always begins with *

If a common target name (TARG1 in the above example) is used, the positions will be traced together to show a route over time. Otherwise, it will be assumed that the targets received represent separate remote GPS units, and will be plotted as such. Note that the target number is not used for this purpose - it is ignored.

If a target status of S is received, Terrain Navigator Pro will indicate an SOS/distress situation; otherwise the target status is ignored.

Other NMEA Sentences
When tracking using TLL messages, the NMEA WPL sentence is available for sending waypoints (markers) to Terrain Navigator Pro. Use standard NMEA formatting to accomplish this. However, it is not possible to transmit or receive routes or tracks from a NMEA tracking GPS.

The NMEA TXT sentence is available in both tracking modes to receive text messages from the remote GPSs. Use the following formatting of
to accomplish this:
TXT - TXT protocol header
01 - Total number of messages in this transmission (not used/ignored)
01 - Message number in this transmission (not used/ignored)
TARG1 - Target name associated with this message; should match target name in TLL or waypoint name in WPL (Note: this is a repurposed numeric field)
Message - Text of message for Terrain Navigator Pro to display.
*35 - Checksum data; Note: always begins with *

Testing the NMEA Tracking Module

If the NMEA tracking module is not displaying positions, here are some troubleshooting tips:
1. Ensure that the COM Port and Baud Rate in the GPS Setup window are correct. The COM Port must match the serial port (either real or virtual) that the base station is plugged into on the computer. The Baud Rate (in Port Settings) must match the baud rate that the base station is transmitting.

2. If using a USB to Serial Adapter  be sure that you have downloaded and installed the latest drivers for that device. Also, be aware that use of a high-quality USB to Serial adapter is strongly recommended. MyTopo has received numerous reports that USB to Serial adapters sold at "Radio Shack" are not capable of properly handling NMEA sentences.

3. Be sure to open the GPS menu and choose Connect before receiving NMEA transmissions. Otherwise, Terrain Navigator Pro will not be ready to receive them, and they will be ignored.

4. Check that the PC is receiving NMEA sentences from the base station. Either use the Show Streaming GPS Data option found in the GPS, Utilities menu, or HyperTerminal/MTTTY to ensure that NMEA sentences are being received. If Show Streaming GPS Data, HyperTerminal, or MTTTY do not show any streaming text when a position should be received, the connection issue lies outside of Terrain Navigator Pro. Please note that MyTopo Technical Support can not troubleshoot connection issues that lie outside of the software.

5. Once you have verified that the PC is receiving NMEA sentences, ensure that they match the specification published above. Improperly formatted WPL, TLL, and TXT strings will be ignored. Refer to the documentation that accompanied the device generating the NMEA sentences for assistance with proper formatting. Please note that MyTopo Technical Support can not assist in the programming of devices that generate NMEA sentences.

6. If the device that is transmitting the NMEA sentences can not add the proper checksum values (*71, *67, *35 in the above examples), open the Advanced options in the GPS Setup window and choose Ignore Checksum.

7. If possible, use a known good application or transmitter to send a test sentence to Terrain Navigator Pro. For example, each of the sample strings in the above documentation are formatted correctly and will cause results in Terrain Navigator Pro. However, the coordinates are located in New Hampshire and will not display unless that state is installed. However, since the TXT message does not include any coordinate information, it can be used to test Terrain Navigator Pro's NMEA tracking connection. Either use the sample provided above, or: $GPTXT,,,TARG1,Testing 123*38

Related Technical Documents

Connecting a Serial GPS to a USB Port
Using MTTTY to test and verify the GPS connection
Sharing a single GPS with 2 (or more) applications

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