AB Line issues

  1. When I lose my rtk signal the AB line jumps about 50 cm one way. Is this normal ?

  2. When I drive my first pass the tractor stays 2in to the right of the line and does nothing about it. Then on the opposite pass it drives 0 error…then repeats 2in again then next pass 0…if this was a WAS issue wouldnt it be off on every pass??

Im using Version 4.3.10 and the INO released with that version. Ntrip is rtk2go with my own base

i’m not good at this but the first questing i would think that if yours correct position is a bit of to the position you have learn the basestation is on. Then your basestation always send message to the tractor for move it 50cm the west for example and then when you lose it you go back to no corrected position. But i just guess.

Sekond question i don’t know :slight_smile:

Casemannen are right about q. 1
Q. 2, lots of possibilities. Do you have any IMU for roll?
If IMU, turn it off, until you find what causes problem.
Are was at correct zero?
Are you on side hill?
Does implement drag to side?

Not using IMU or Roll Was was set to zero on flat concrete using measurements to align wheel perfectly straight. Field is flat. Planter drift is very likely the cause but i feel it would pull one way constantly not matter what direction i was going.

I did survey in on my base for 24hrs then used those coordinates so maybe that is not accurate enough ?

The base position will not affect this pass to pass issue.
But you say you made WAS Zero holding still on concrete, I don´t think that is good enough, You must drive in a straight line watching WAS number in the steer setup window. It must be Zero when driving AB line (on a flat field with no implement in the ground)

I find the most accurate way to adjust your WAS zero is to engage auto steer and drive straight while watching the horizon and adjusting your zero position. Works the best on a long enough field.


Is the 2in to the right the number you read on the AOG screen, or are they 2in to the right of line on ground/field?

And you are right maybe not a WAS issue (when my WAS were 1 degree off, the tractor was always 4 inches to the right of line on screen) I compensated with moving Antenna 4 inches the other way in tractor setup, and seeding matched correct. (could have corrected ino instead)

The light bar indication shows 2in off and never tried to correct itself. Then on the next pass it stays between zero…then the next pass back to 2in off and the tractor does nothing about it. I feel if it was a WAS issue it would be 2in off no matter what direction I was going. Ill try resetting the WAS by driving straight instead of measuring. Also I have a Brick IMU mounted on the roof but it is turned off do you think i should be using it ?

So if I make and AB on flat ground …engage autosteer then adjust WAS zero till the light bar at top shows zero ? Tractor is JD 4555 two wheel drive pulling 12 row JD 7200 planter. I think alot of the issue is tractor cant steer as well in loose soil while pulling an implement.

I do not use IMU
Better way to set WAS is the one m_elias posted.

I would set WAS so draft would be same in both directions, then compensate either by implement offset or antenna offset (I found antenna offset worked best for me)

I will do that and see if it solves this issue appreciate it thank !

By engage autosteer do you mean drive an ab line ?

I should have been clearer, I used the Steer Settings drive test, set to zero WAS, then I adjusted the WAS zero setting until I could see it was driving straight.

ok great thank you

How do I fix this do I need to re survey my base station location ?

Hmm. Nothing you can do to fix that, it´s the way RTK works.
Satellites move all the time, so if you drive in single mode (only rover GPS) you can see (if you return to same spot in field about one hour later) that the line have moved 20 to 40 cm.
With RTK the base would see the satellites have moved 20 cm and tell rover to move same distance

I’d say almost correct. No way to avoid a position change when losing RTK and moving to autonomous or SBAS corrected mode but the average change (error) is larger if the surveyed base location is incorrect.

Better to have an absolutely accurate base location (to a couple of cm or so) but the loss of RTK fix is the real issue. Almost useless to drive with autosteer if RTK fix comes and goes.

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That makes sense was just making sure I wasn’t missing anything.

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From my understanding, an absolute base position is only really needed if you plan to change base stations or move your base station for the same field. If you always use the same base and it doesn’t get moved then any reasonable position will provide good RTK correction.

Correct but here the issue was when losing RTK fix. In this case it is not about changing between base stations but changing between the position obtained with the RTK base versus the position in autonomous or SBAS mode. If the base is surveyed 10m off, there will be a big jump from RTK fix to SBAS.

Then again, as I said previously, there are other significant issues if RTK fix is frequently lost. Better to aim at a reliable RTK fix, then there would be no issues from inaccurate base location (when running from a single, fixed base as most do).