The National Marine Electronics Association is the US based trade organisation which sets the standard for interfacing electronic devices. Founded in 1957 by a group of electronic dealers the association was intended to strengthen their relationships with the marine industry, including the US coast guard and the FCC. The digital data exchange signal that bears its name was only created in the early eighties as the need to transmit positional data to marine devices increased. Today the signal is used across many devices from sonar buoys to GPR equipment.
Of the Leica range of GNSS equipment only the GS10, GS14, GS15, GS16 and GS25 can export an NMEA message and even then, it’s not a standard option aboard the sensor. You’ll need a specific license key loaded on the sensor to get that stream running.
Once you get that sorted you can set up the message. There are three important aspects to getting this right, choosing the device you want to use, picking your Talker ID and choosing what message/s you want delivered.
You’ll get several options from the dish for the device you can use but you’re probably going to export it by cable from a port on the dish or use the Bluetooth connection. Either way you’ll need to edit the device and check the baud rates are correct for getting the data into your device in a timely manner.
Your Talker ID can be important as it’s the prefix attached to each message and if your device is expecting a specific ID it won’t accept anything else. Older devices probably expect the ID GP (for GPS) but more recent devices might want the ID GN (for GNSS).
Then pick your message. Most devices are happy with just a GGA which will give you Lat, Long, elliptical height and the RTK status but there are a host of others that provide more information.
What each message means
- GGA - Global Positioning System Fix Data
- GGK - Real Time Position with DOP
- GGK-PT - Real Time Position with DOP, Trimble Proprietary
- GGQ - Real Time Position with CQ
- GLL - Geographical Position Latitude/Longitude
- GNS - GNSS Fix Data
- GSA - GNSS DOP and Active Satellites
- GSV - GNSS Satellites in View
- RMC - Recommended Minimum Specific GNSS Data
- VTG - Course Over Ground and Ground Speed
- ZDA - Time and Date
- LLK – Leica Local Position and GDOP
- LLQ – Leica Local Position and Quality