Topcon x25 GPS Heading is not working

DavidHammond123

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I've got a Smart7 GPS plugged into my Topcon x25.
The x25 can read the GPS fine, getting satellites, position, and speed into the x25 all correctly.
But the heading is completely wrong, the heading is stuck at random headings, will occasionally move around but doesn't actually ever line up with the correct direction I'm actually driving.
No idea what is going on with it, sometimes it seems like the x25 will turn around to the heading but then it gets stuck and doesn't update as I turn.

Has anyone seen this before? Or do they know the fix?
 
Location
North
You might clarify some background. Smart7 sounds to me like a Novatel Smart7. Is there a Topcon Smart7? Or are you running the X25 from "a foreign" GNSS receiver?

Do you mean the Topcon X25 map view is not aligning with the tractor heading or is the tractor heading on the screen off from the way it actually approaches the wayline?

If you are using a Novatel GNSS receiver, which NMEA messages are you feeding to the X25?
 

DavidHammond123

Member
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You might clarify some background. Smart7 sounds to me like a Novatel Smart7. Is there a Topcon Smart7? Or are you running the X25 from "a foreign" GNSS receiver?

Do you mean the Topcon X25 map view is not aligning with the tractor heading or is the tractor heading on the screen off from the way it actually approaches the wayline?

If you are using a Novatel GNSS receiver, which NMEA messages are you feeding to the X25?
Yes we are using a Novatel Smart7 (I've also tried some NMEA/GPS simulators plugged into the x25 and are having the same issue).
So it is a Novatel Smart7 plugged into the Topcon x25.
Topcon x25 is set up to use a generic NMEA GPS in its settings, it has the correct COM port assigned, and the correct Baud Rate (19200) to match the Smart7.
The Smart7 is set up with 19200 baud rate, and set up to output GGA (5hz), VTG (5Hz), and ZDA (15s) as that is what the x25 manual requests (plugged the Smart7 into our PC and confirmed it is sending those messages).

On the x25 screen we can see the correct number of satellites, DGPS, the correct latitude and longitude, and correct speed.
Our issue is not that the map is not aligned with the tractor heading, it is that the heading reading itself is incorrect.
Basically, our tractor on the map is 'crabbing' across the map as we drive. The heading reading on the bottom of the screen and the direction of the tractor on the map are both wrong.

So for example we have driven around our yard in circles and different patterns and the heading just does not update (neither the heading value on the bottom of the screen or the tractor on the map).
The tractor's position does update but it will always just be pointing at a random heading which doesn't represent reality. The heading will just be stuck on a random value like 27 degrees, then every once and a while (not regular) it will update the heading a bit and almost seem correct but then it will get stuck again.

We have tried to change the output messages of our Smart7 and NMEA simulators in several different combinations and it always has this issue, not sure if this is something anyone else has run into.
 

DavidHammond123

Member
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Ok so we have figured out how to get it to work correctly with the Smart7.
We did 3 things and then the Topcon x25 was happy with the Smart7 GPS heading:
1. We reduced the configuration of the Smart7 so it was simplified down as much as possible and just had SBAS set up and the basic NMEA strings.
2. We moved the Smart7 onto the bonnet of the tractor, we had originally temporarily stuck the Smart7 on top of the drill's hopper, behind the tractor. (Since it was behind the rear wheel axle if we turned right the GPS would actually move left which we think was a big problem).
3. We updated all the dimensions of the tractor and GPS position in the Topcon x25 screen to correctly match the new position of the GPS.


We think the algorithm in the x25 which was looking at the GPS position/heading and using the dimensions to translate that into where the tractor is sitting was getting very confused by what was going on with the GPS being behind the rear-axle so its position/heading would be inverse of the actual tractors heading when we make turns.
 

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