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Leica viva NMEA output: $GNGGA vs. $GPGGA?

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GNSS & Geodesy

Last Post by niko23 7 years ago

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BigWill

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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*36

Possible 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?

Posted : October 5, 2015 9:02 am

mathteacher

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This link addresses the problem for Hemisphere. Near the bottom of the page is an additional information section. Click on the JNMEAGGAALLGNSS link in that section. That may give you a clue as to how to proceed.

GPGGA

Posted : October 5, 2015 11:04 am

BigWill

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[USER=7674]@MathTeacher[/USER] : Yes, that is exactly the type of answer I need if I were using a Hemisphere receiver! Thank you.

That option must be available through the Leica Viva software, hidden in a menu somewhere...

update: after looking at MathTeacher's reply, I found this document online for Viva: http://spatialtechnologies.ca/wp-content/uploads/2012/04/GS-NMEA-Settings.pdf

It seems like it may be the mysterious checkbox "use a defined talker ID." I will explore this and post what I find tomorrow.

Posted : October 5, 2015 11:19 am

mathteacher

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Sometimes a note from one manufacturer will help with another. Maybe this one will be more helpful.

http://spatialtechnologies.ca/wp-content/uploads/2012/04/GS-NMEA-Settings.pdf

Posted : October 5, 2015 11:44 am

BigWill

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I just wanted to follow up on here regarding the issue I was having with the GGA string. Just in case anyone is using Leica Viva and needs a Leica GNSS sensor to output a $GPGGA string, and then stumbles across this post like I have stumbled across so many answers on this forum:

The Leica Viva software allowed me to change the first 2 letters in the string, effectively changing the $GNGGA string to a $GPGGA string.
In the NMEA Output screen, "use a defined talker ID" must be selected, then in the box, specify talker ID as "GP." That changes the first 2 letters of the string, so that it now reads $GPGGA.

Thanks for your help, MathTeacher!
W

Posted : October 20, 2015 10:11 am

Christian

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BigWill, post: 341147, member: 9205 wrote: I just wanted to follow up on here regarding the issue I was having with the GGA string. Just in case anyone is using Leica Viva and needs a Leica GNSS sensor to output a $GPGGA string, and then stumbles across this post like I have stumbled across so many answers on this forum:

The Leica Viva software allowed me to change the first 2 letters in the string, effectively changing the $GNGGA string to a $GPGGA string.
In the NMEA Output screen, "use a defined talker ID" must be selected, then in the box, specify talker ID as "GP." That changes the first 2 letters of the string, so that it now reads $GPGGA.

Thanks for your help, MathTeacher!
W

Thanks for your post BigWill, it was very clearing. I tried to do as you say. I was able to configure the GS15, but the SIR3000 did not get/recognize lat and lon. I set a rate of 0.1 s, but am not able to alter any parameter on the GPR. As i read it will be necessary a data logger to manage to write the right position for each pulse.

Thanks even so.

Posted : November 12, 2015 2:17 pm

BigWill

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Christian, post: 344122, member: 10770 wrote: Thanks for your post BigWill, it was very clearing. I tried to do as you say. I was able to configure the GS15, but the SIR3000 did not get/recognize lat and lon. I set a rate of 0.1 s, but am not able to alter any parameter on the GPR. As i read it will be necessary a data logger to manage to write the right position for each pulse.

Thanks even so.

Christian,
Yes, this was pretty frustrating, which is why I decided to post the answers on here so others could find them.

First off, your Leica system has to be running the Viva PRO version to output an NMEA string. Of course, that as extra money$$.. Have you confirmed that your Leica is outputting an NMEA string? Try downloading VisualGPS software onto a computer with a serial port to verify. That is a free download available here: http://www.visualgps.net/visualgps/

The SIR3000 manual has a little section on GPS: http://www.allied-associates.co.uk/pdfmanuals/sir-3000%20manual%20revb.pdf

Also, a refresh rate of 0.1Hz might be too much. Try a refresh/signal rate of 1Hz in the Leica settings and see how that works.

Good Luck!

Posted : November 12, 2015 2:40 pm