Leica viva NMEA output: $GNGGA vs. $GPGGA?
Hey Guys,
We are having a tough time getting a Leica GNSS unit to export a $GPGGA string so we can import RTK corrected coordinates to our GPR (Ground Penetrating Radar) equipment.
Our eventual goal is a geolocation within a few cm horizontal, and a vertical to within 10-20 cm or so. The idea is to get a real-time topographic correction while we are doing long (a few km) GPR surveys, and a good horizontal fix as well. Precision of an RTK will work fine for this and might even be overkill. The problem is getting everything to speak the same language.First, some technical specs and things I tried:
GPS: Leica GS14, with CS15 Controller, receiving network corrections via cell. This is a GNSS, receiving GPS and Glonass satellites. *We had to upgrade to the Leica Viva PRO to activate the ability to export NMEA strings, and have a Lemo to serial cable supplied by our local surveyorÛªs equipment boutique shop. Leica is indeed streaming an NMEA string (confirmed by running VisualGPS software on a laptop).
GPR: Swedish-made Mala GPR units. We have approximately 4 different GPR configurations I have tried this on.. This says it requires a serial port inputting NMEA 0183 and $GPGGA string. The GPR systems do accept NMEA strings, and did so quite readily when we borrowed a Trimble ProXH antenna a few months back.Serial ports: The baud rates and other serial port requirements are matching across all equipment, and even tried several different settings, making sure they matched in both GPR and GPS software.
Rates: I also tried different fix rates. The Leica will send a location at up to 20 Hz, GPR software accepts strings at up to 5 Hz. I tried 5 Hz, 2 Hz, 1 Hz and 0.5 Hz, with no good results.OK, on to the problem:
MALA software engineers are saying they need a $GPGGA string, but Leica is outputting a $GNGGA string. The way I understand it (correct me if I’m wrong), $GP means we are using a GPS only system, and $GN means we are using a Glonass enabled GNSS system. GGA just means that this is location data.Sample NMEA string from the Leica while RTK is initialized, captured by the laptop:
$GNGGA,185824.00,2605.0247881,N,08014.3097082,W,4,14,0.7,-24.343,M,,,0.59,0402*36Possible Solutions(?):
1) Is there a setting somewhere, where I can make Leica Viva export a $GPGGA string?
2) Is it unreasonable to suggest that the GPR software developers should allow a $GNGGA string? What happens when the European constellation comes on line, another GGA string format?
3) Does a different brand (Topcon, Trimble, etc) GNSS receiver export $GNGGA strings or $GPGGA? Lucky for us this Leica is a rental, to test feasibility of our survey design before buying one- that means if we need to switch brands we can. I do prefer to support the Leica-dominated local surveyorÛªs equipment boutique shop, but I also like all of our expensive equipment to work togetherÛ?.Maybe someone on here has run into a similar issue?
Log in to reply.