Setting up the base on a new location every day/half day to right away

Q&A forumCategory: QuestionsSetting up the base on a new location every day/half day to right away
floflo asked 8 months ago

hi.

I’m planing on ordering a simplertk2b kit but for agricultural use. I expect the range of the LR kit to be too degraded in the moderately hilly with three-line and small forest environment i plan to use it in.

The obvious solution (at leat to me) would be to use a MR kit instead and set it up at the corner of the field, but reading and dinging into this forum I’m getting more confused than getting answers after reading about time mode and moving bases actually are on the rover and so on!
So here i am with my couple of questions:

-I think i know the answer but does the LR kit require both modules to be in direct view to work with the range of 10km announced?
-What configuration is required for the base to work without issue, basically waking up in a new place every time it’s turned on?
Do i have to use the fixed base configuration and set the coordinate manually every time i change place (how accurate does this coordinate would need to be? can i pick the coordinate from google maps set the base about there once on site drive a post in the dirt and use it as a support for the base hence giving me repeatability as a side benefit)

or is there another function ( moving base? ) that allow it to cope with the constant relocation and still perform with a sufficient accuracy (something “rtk ish” below 5 or even 10cm but getting reed of signal drift/accuracy drop in the middle of a half day job)

I listening to your suggestion!

Thank you.

AndrewRL replied 8 months ago

Are you worried only about relative accuracy during a job – ie “pass to pass accuracy” eg so you can skip swaths on the first pass over the field to make turning easier at the ends and fill in the gaps later in the day knowing that everything will join up OK?

Or are you looking for repeatable positioning for example to use A-B guidance lines from drilling to do the spraying and fertilizing later in the same season (perhaps with autosteer) and/or to use the same field boundary lines from year to year?

This will affect the advice you need from Ardusimple.

Ardusimple Staff replied 8 months ago

(floflo) -I think i know the answer but does the LR kit require both modules to be in direct view to work with the range of 10km announced?
(ardusimple) yes

(floflo) -What configuration is required for the base to work without issue, basically waking up in a new place every time it’s turned on?
(ardusimple) The default configuration will work in this case, but every time you move it and power-down power-up the base will need 10-15min to calculate its position and start working again. Alternatively you can also set the position of the base manually if you know it. The problem with this setup (changing base station position or setting more or less its position manually) is that you will only have pass-to-pass accuracy for every base station installation, but not pass-to-pass when you move the base station and want to continue from the pass from a previous base station installation.

(floflo) or is there another function ( moving base? ) that allow it to cope with the constant relocation and still perform with a sufficient accuracy (something “rtk ish” below 5 or even 10cm but getting reed of signal drift/accuracy drop in the middle of a half day job)
(ardusimple) This would allow you to accelerate the time to start for each base station installation, but it has more error than a base station setup.

floflo replied 8 months ago

Good to know the base will adapt itself on default configuration, the mater about not turning it on before setting it properly and the 24h to get centimetric accuracy had me think otherwise.
What about this 24h thing BTW?

2 Answers
floflo answered 8 months ago

Yes just as you guessed it! skipping passes or not, the goal is to work with no worries of the AB line or reference line moving around during the job and eventually in case i skip passes coming back next to the reference pass and ending up at the right place.

AndrewRL replied 8 months ago

I would suggest trying the first solution first and provided that you don’t power down the base during a job this should work fine. if you are not worried about reusing the A-B line on a later date you can adjust the parameters to shorten the survey-in time,

I have heard that some tractor navigation boxes don’t work well with moving base mode. This mode is mainly used for particular technical applications where the base IS ACTUALLY moving (not just portable).

Another method which I have not tried but should work if your navigation solution only ever shows you one field at a time – you could use static base mode set with some arbitrary fixed location and leave it the same regardless of the position of the base. Then you could move the base from stake to stake, but provided you select the right field on your navigator (and provided the base is on the right stake) you should see your saved A-B lines and boundaries all show up on the screen with the tractor in the right place in the field. Powering on off the base would not be an issue. You would not be able to see a whole farm view because all the fields would be in false positions and overlapping but if all you want is navigation then this won’t matter and would be repeatable year to year.

Alternatively if line of sight is a problem for radio – do you have reliable 3G (or better) mobile coverage and sensible data charges?

If so you could forget the radio links and use the internet to transmit corrections.

Fix the base in a “good sky” location at your farm and use the “wifi NTRIP Master” on the base station simpleRTK2b to stream corrections to rtk2go.com.

At the tractor (rover) end there are a few options. You could use the Bluetooth Xbee and use a smartphone to get the corrections (I have found the Lefebure app on Android works well), or you could use another “wifi NTRIP master” and have a wifi hotspot in the tractor (smartphone or mobile-wifi box) or I think there are Xbee 3G or 4G boards.

You need to consider how you will use the position to navigate. Are you planning to use an Android App (if so the Bluetooth option work well and with “mock locations” set can works with a variety of apps) or are you planning to use a brand name navigation box (if so you will need to consider how you are going to get RS232 out) or if you are intending a homebrew solution like AOG then that has an NTRIP client built in and you can connect the SimpleRTK2b to the windows tablet by USB.

floflo replied 8 months ago

Good to know the base will adapt itself on default configuration, the mater about not turning it on before setting it properly and the 24h to get centimetric accuracy had me think otherwise.
What about this 24h thing BTW?

I’m using AOG so it’s supposed to go well via USB (finger crossed)
The 3G service here is quite solid but i expect holes and we are charged crazy prices for data the xbee radio kit is cheaper on the long run and don’t rely on 3G coverage.

I’m interested in the possibility of using the base with determined coordinate identical for all field, but I’m not sure if the base will work if the position it get is from gps km apart from what it’s set for.
Guess It would be as repeatable as i accurately put the base at the same spot every time ex: right on a cornerstone and also reduce the delay to get a accurate connection.
Would it blindly make a 3KM correction? or do nothing as it detect an error because life can’t be the easy right? did someone try or do Ardusimple know?

Wolfgang answered 8 months ago

Two more possibilities:
 
Multiple bases
 
Set up multiple bases that between them cover the whole field, each transmitting their own correction. You will need to set a different base ID for each station in the RTCM stream. From memory, I do not recall the F9P having a command that allows you to do this, maybe someone can clarify?
 
XBee mesh mode
 
Instead of multiple bases, buy extra XBee radios and set them up so that between them cover the whole field *and* have comms with at least one other XBee unit. Then review the XBee configuration, ensure that they are in mesh mode and tweak as required. Depending on the size of your field and radio coverage you might need to notch down the correction rate to 0.5 Hz if that’s still acceptable in your application.
 
 

Ardusimple Staff replied 8 months ago

The challenge with multiple bases, is the areas where the simpleRTK2B will receive corrections from 2 bases at the same time. In this case, it will mix corrections and behavior is unpredictable. The correct way to do this, is to add an application processor which decides which is able to split the data from 2 base stations and send to zed-f9p only the closest one.

AndrewRL replied 8 months ago

@floflo You would have to check with Brian Tee as to how AOG would cope with all the fields appearing to overlap with the determined coordinate being identical for each stake. I cannot see it being an issue if you are only viewing one field on the screen at a time.

I don’t think you need to worry about the position being false within reason.

I am sure @Ardusimple will shout out if I am wrong, but as I understand in RTK mode (greatly simplified) all the base does is look at the sky and broadcast to anyone listening saying “I am at X and this is what I am getting from the satellites” (which is not the same as what the satellites transmitted because of atmospheric effects and so on – and that is the main source of drift which we are trying to eliminate,).

All the rover does is look at the sky and says “oh look my signals are slightly different so with some iteration and complex maths that must mean I am Y away from the base, therefore I must be at X+Y = Z”. All in 3D of course. And because the rover is reasonably close to the base the atmospheric effects will be the same and cancel out – which is the main reason why accuracy decreases with distance from the base, but the F9P can compare what it is getting on the two frequencies eliminate some of that effect.

So neither the rover nor the base know or care whether X is right in the real world, they both implicitly trust you set it correctly. If without moving the base or the rover I adjust the base coordinates by 100m north, all that happens is that the rover obediently reports that is it 100m north. Nothing breaks. If it is 3km then likewise.

Of course nothing is ever fixed in the real world because of continental drift and so on but this mechanism is what enables RTK to give apparently constant positions. So in Europe a surveyor will generally not set the base coordinates using the latest iteration of the world WGS84 datum but instead he will use different ones according to the ETRS89 datum which is artificially fixed relative to the Eurasian continent, and the rover has no choice but to report its position relative to ETRS89 too and will be oblivious to the continent drifting around. In South America he would use a SIRGAS datum instead, and so on.

In your situation you will have coordinates relative to your “floflo datums” which is fine for tractor driving unless you want it to mean something in somebody else’s world. Let us know what Brian thinks.

On @Wolfgang’s suggestion there was some talk about Ardusimple testing their LR module in repeater mode which might work if you had more than one set of farm buildings within line of sight to get you further or around forests but I never saw any outcome.