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tmatt 07-09-2019 10:54 PM

Ardusimple RTK Questions
I am very new to the idea of do-it-yourself GPS. I currently have an Ag Leader Intregra with a OnTrac 2+ steering system that I run on WAAS with a GPS 6500. I have been wanting to upgrade to RTK precision and have been reading up on the Ardusimple units. I am blown away by the price that they sell for compared to the big name stuff. It seems to good to be true. Are there any limitations to the Ardusimple setups?

I am a small farmer with fields located close together. My goal is repeatability year to year. I am considering the Long Range kit and have no problems building permanent spots to return the base to year to year if the range is not far enough for one point. I have read up on how to connect to the serial output, but is it pretty much plug and play after that?


BrianTee 07-09-2019 11:10 PM

Are you hoping to use the ArduSimple as a base station and the Integra as your rover receiving corrections?

tmatt 07-09-2019 11:15 PM

I was planning to get the ArduSimple kit with a base and rover to feed into the Integra. Here's the link to the kit I'm looking at....


torriem 07-09-2019 11:34 PM

Can the OnTrac 2+ accept GPS from an external source and use it for steering? Is there a serial input port on the OnTrac? EDIT: I think so. The manual states it's compatible with most GPS receivers, so as long as you give it the proper NMEA sentences, it should go.

I believe the ArduSimple kit can probably work for you but will require some assembly. What I mean is that it's just a bare board. You'll have to put it in an enclosure, and provide a TTL to RS232 converter to convert the serial output to RS232 to feed into the OnTrac. Also you'll have to use the u-center computer program (which is a bit hard to use) to configure it to output the NMEA strings that the OnTrac requires (which I don't know but could guess at), and set the serial port speed.

The base station unit will need a bit of configuration as well to enable survey-in mode (or if it's never going to move, fix it's coordinates).

If you can do this, or get someone to help sit down with you and set it up, it could work!

m_elias 07-10-2019 12:50 PM

55 Attachment(s)
The kit will come ready to use except as torriem mentioned, the base position (timer3 setting) can be changed from survey-in (default?) to fixed if you know it's absolute coordinates. I'd also change the default update rate of 1000 ms (1hz) to 200 ms (5hz) or 100s (10hz). I expect the default nmea outputs will suffice but you could probably turn a bunch off. Does your display's manual say what sentences it wants?

Edit. And as was also already mentioned, you'll need a TTL to rs232 adapter. And a 12v to 5v power adapter for the arduSimple in the tractor.

tmatt 07-10-2019 11:26 PM

Thanks for all the help!

How do you determine the absolute coordinates of the base station? All our fields are within one mile, but there are some tree lines that I was concerned would affect communicating back to the base. Is it possible to have multiple location points to move the base around to?

Regarding the GPS sentences for the display, I found this in the Ag Leader manual. Is this do-able with the ArduSimple?

. At present, the display only requires two NMEA Message formats: GGA and VTG.- GGA: position in longitude and latitude.- VTG: ground speed - GSV, GSA: required to view the Satellite Plot, but are not required for GPS information.- GLL, ZDA, RMC, MSS: Leave these other NMEA message formats unchecked, unless you are connected to a third-party monitor and have been directed to do so.

m_elias 07-11-2019 09:20 AM

If you want an accurate absolute position, I believe you need to get it surveyed by someone who knows what their doing. I just used Google Earth's number. To change your base's fixed position value, you have to change it with u-center or figure out how to do it via UBX commands on a serial interface.

By default, you'll get those 2 messages and a few more. To turn off the extra, connect with u-center, open the configuration view, go to the messages page, and selection each message that you want to change from the drop down menu and check/uncheck the ports as needed.

torriem 07-11-2019 10:52 AM

Even if you set want to set a fixed base position with u-center, you can still use survey-in mode to take a bunch of readings over several minutes and average them together, which you can then write down and put it as a fixed position for next time.

For a mobile base station that you set up on a fence post, survey-in is probably your best option. My base station is sort of fixed at the moment, and I just use survey-in mode for now. When I get it permanently mounted somewhere then I'll probably just do a survey-in to determine the approximate location and hard code that in. I only really care about my own accuracy and repeatability, not that I'm exactly the same as my neighbors.

tmatt 07-11-2019 11:14 PM

Great information, thanks guys!

What kind of accuracy and repeatability is possible with the survey-in mode? Is this capable of sub-inch accuracy?

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