GPS errors/jumps

GPS / RTK / GNSS
#1

I am having sudden jumps on GPS position (at least I think it is GPS that causes sudden jumps). Maybe once in a couple of minutes position jumps ½ meters up to 6 meters sideways. If autosteer is on it causes sudden jumps on the driver as steering wheel goes wild.
Is it caused by bad GPS weather or something? At spring seeding it was also really bad and problem went away during the day. I didn’t have hardly any problems during summer spraying. Yesterday and today sudden errors occured randomly.
I have ardusimple simplertk2b receiver and RTK base station.

Anyone else have this kind of problems?
Is there some kind of filtering on aog code?

Roll affecting heading
#2

maybe you lose the RTK correction and get back to no RTK, but you haven’t the RTK alarm active so you not notice when you lose it? :slight_smile:

#3

RTK alarm is on. Seems like there is only one error in location then it returns right back.

#4

What kind of roll do you use?
AOG calculates the line based on roll number and GPS antenna hight.
You can check roll issue by setting antenna hight to zero.

#5

Are you using the version of AgOpenGPS that shows you how old your rtk correction data is? What max differential correction age setting are you using in your f9p?

#6

If you loose RTK, and have SBAS enabled you will jump. Disable SBAS WAAS is not worth the problems.

#7

SBAS was enabled. I newer experienced jumps if RTK was lost.

#8

I thought it could be a heading issue. But roll issue, how I didn’t think about that. This could actually be a roll issue. I will try it today.

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#9

Do you always use the exact same base coordinates and location?

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#10

Do you mean RTK base station? Yes.

#11

The beauty of custom hardware and software. You newer know where the problem is.
Within long day of harvesting.
Disabling SBAS didn’t make a difference.
It doesn’t seem to be a roll issue.
Part of the problem seemed to be heading issue. What I remember from the spring seeding. One major problem was that sometimes during the jumps tractor on the screen stuck to reverse. That is the reason I disabled reverse detecting on later versions.
During the day I set heading to 100 % GPS. Is 100 % GPS really 100 % GPS heading or just mostly GPS? It was quite difficult to follow whether jumps happened on sudden IMU heading changes.
Later I set IMU heading to constant 0. any big jumps didn’t happen anymore. However there just little time to test that.
Small jumps (about 30 to 60 cm) still happened. Could it be just some low orbit satellites hiding behind the tree on the horizon? Distance to the RTK base station was about 2-3 km.

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#12

The only jumps I’ve experienced have been because I lost rtk signal for too long but then I have not used an IMU yet. We are on relatively flat ground. Can you unplug your IMU and see what happens then? I asked earlier if you are using the newest AoG which shows differential correction age

#13

Oh, I totally forgot correction age. I haven’t even noticed that before.
At moment GPS is not connected and Age says 0.5. What is good and what is bad number?

Rain should come so it might take days to get back on the field.

#14

With a good RTK connection it should stay below 5 seconds but in my area it seems okay if it goes up to 30-60s depending on how accurate you need your GPS to be. I have my F9P set to hold RTK with correction data as old as 250s (pretty much the maximum setting) to minimize those jumps and I set the differential age alarm to 20s. This way I don’t lose RTK fix but I know if my RTK connection isn’t working and the rtk correction data is getting old.

#15

Maybe you should play with the fix to fix distance settings. I found the standard is too low to make tractor steer straight.
That is more visible when IMU setting is at mostly gps
One more thing: in this thread I don’t see that you have f9p set to output at 8 or10 Hz. This problem you have could also be gps signal set to only 1 Hz
1 Hz is fine for ntrip but not enoug for AOG nmea

#16

Where in Ucenter can you set the maximum time to hold RTK correction, and how do you set an differential age alarm?

#17

Without loading up u-center I don’t know where exactly the setting is. The newer versions of AoG have that option in the settings.

#18

I did get a little bit of harvesting done before rain came.
Antenna Heading Type was set to VTG. I didn’t notice a difference Fix and VTG before. What does VTG even mean?
I set Heqading to Fix and Fix Trigger Distance to 1 m. And I completely disabled IMU. Not a single jump happened. Only time there was a bigger jump when I set Fix Trigger Distance down to 0.5 m while moving.
Whenever there was a bit uneven ground it made a bit of wobble. Wobble seemed to be bigger on screen that tracks looked like. Enabling roll stabilized movement. Unfortunately I had only a few minutes to test with roll enabled before the rain hit.

Every time I looked RTK Age stayed under 2.

F9P output is set to 10 Hz.

Thank You all for help.

#19

I think VTG is a message coming from the receiver.
So it would take the heading angle calculated from the receiver. With single antenna and RTK it’s way better to use fix to fix.

#20

Hello,
How do you set the maximum correction data age in F9P?