Absolute / relative heading

Goodday everyone. Now have AOG with a configuration of Ublox F9P, BNO055 (heading) and MMA (roll). The problem I have now is that AOG does not immediately know when it is standing still which direction it is heading. Only after a certain distance can he estimate this.
If I understand correctly, AOG uses the BNO with the Euler function and that produces a relative value and not an absolute value. At startup he starts at 0 and then looks at the deviations.

Because we want to use AOG for very slow plants and then have no room to drive a bit for measuring with multiple fixes, we need to know the right orientation right at the start.

In short, do you know if anyone has a setup with an absolute heading sensor?

it is coming from ardusimple with 1/2020. working with 2 antennas…

Nobody use the BNO055 in COMPASS mode?

the compass of the imu has a drift and is not pointing to the relative north.

so it is only possible to use in this way. maybe brian can find a way of adding more information of the compass when start driving…

The BNO never really knows where it is with a lot of soft iron around it, while there are much better solutions, they are also $$$$$. The best solution is as Andreas mentioned, the dual antenna setup which will probably cost less in the end and much better heading.

Without a really good compass, direction can only be determined once you are moving.

Anybody know if 2 cheap eBay drone type gps receivers keep relative position, when sat at a fixed distance apart (only for directions)?

When I first got my BNO I tested it with the standard Adafruit librarys on my office desk. the office is full of electronic and electrical kit so I didn’t expect good results. Also, as an additional test I had a full box of nickel / iron cast welding rods (£300!! :sob:) to act as a disruption. On power up it called it’s present orientation due north and was reasonably steady, then after some movement it re calibrated to indicate absolute orientation. To disrupt this steady output I had to get the box of rods (5Kg?) within about 100 to 125mm of the BNO and even then it only moved the correct north a few degrees until it was really close.

When I’ve tested AOG with my stripboard pcb I’ve noticed the display spins wildly on startup and the gps heading is all over the place however the BNO output is very stable.

Just my observation. My properly installed system is going in very soon so it will be interesting to see how it performs.

Try to zero roll and restart AOG.

The odd thing about the BNO is it always starts up pointing true north.

a little cheap F9 for dual antenna has been released!

Found the simpleRTK2B+heading - Basic Starter Kit IP67 (“https://www.ardusimple.com/product/simplertk2b-heading-basic-starter-kit-ip67/”). Looks this is an simpleRTK2B board with a simpleRTK2Blite board addon, but there is also a simpleRTK2B-F9H, what’s the difference?

I think a dual gps setup is the best solution for us (only 2 gps receivers, no more sensors). Somebody already has experience with this?

We use AOG software with a single simpleRTK2B as Rover. Thx!


The difference is describe here : Freshly baked ZED-F9H is now available at our store - ArduSimple
So what is the difference with the existing simpleRTK2B+heading – Basic Starter Kit IP67 ?
- In our kit, as we are using simpleRTK2B + simpleRTK2Blite, you can read position+heading+relative position being connected to only one unit.
-When using simpleRTK2B-F9H + simpleRTK2Blite, you will read RTK position from F9P unit, and headingfrom F9H unit.

For experience, some discussions here : Dual GPS output format for AOG - #47 by kris


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When using an ardusimple dual receiver setup do all the nema messages from the main reciever have the heading information from the moving base configuration or do you have to use certain nema messages relating only to a moving base setup?


Ardusimple ouput heading information only on UBX protocol, see topic here : Dual GPS output format for AOG - #47 by kris
SimpleRTK2Blite in a multi-rover configuration: How is heading obtained? - ArduSimple


Im having the same problem, very unstable heading, (using m8t with rtklib and bno) the thing is It was working fine until i updated yo the latest version of AOG, i also tweaked the GPS config in the ublox software, the rtk output seems fine, but when i stop the tractor it goes crazy, and when is working Its also very unstable, this was not the case before, ill upload a video later, i dont understand what happend… Ill try to zero the roll and see what happens

I found out what was going on, i’ve been using an offset antenna setup, about -50cm, that offset setting in AOG was messing everything up, i think It has something to do with how AOG translate the nmea sentence to correct the offset, centering the antenna and zeroing the offset setting fixed everything


What is the max offset which can be used without problems?

50 is about max, but you can go about 100cm. I have no idea how the commercial versions make it work.

-50 gave me serious trouble, i tried -45 and it seemed to work just fine, anyways i reworked the antenna mount and centered It to avoid ant trouble

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Hello everybody,

Do i understand correctly, the BNO calculates a relative heading. That means the board has not to be mounted absolutely straigt to the driving direction?
Think it is difficult to match the direction when the board is installed in a terminal box.