GPS Precision Farming Accuracy

[pmsmechanic]

so for those of you who use it, how is the reference station any more accurate, doesn't it suffer from the same ionospheric conditions?

From what I understand the inaccuracies come from the satellite signal being degraded for what ever reason. Probably military reasons but I don't know. The reference station signal isn't degraded and is only used by the owner and whoever he rents the signal out to. You can also pay for varying degrees of accuracy. You need subinch for rowcrop but 6" is good enough for general field work

 

[LittleBill21]

From what I understand the inaccuracies come from the satellite signal being degraded for what ever reason. Probably military reasons but I don't know. The reference station signal isn't degraded and is only used by the owner and whoever he rents the signal out to. You can also pay for varying degrees of accuracy. You need subinch for rowcrop but 6" is good enough for general field work

yea i am reading through it, reference station which is at a known point, sends the correction data to the local receiver, giving it the corrections needed to be accurate, but I have also seen units on a tripod away from the unit that is being used to measure, still trying to figure that out

 

[Williy]

YUP! You can build a tower and set up there and have a cool one while you watch your tractor roam around the field with you little control box

willy

 

[pmsmechanic]

yea i am reading through it, reference station which is at a known point, sends the correction data to the local receiver, giving it the corrections needed to be accurate, but I have also seen units on a tripod away from the unit that is being used to measure, still trying to figure that out

The little unit on a tripod is a portable reference station. Sometimes used for fields that aren't able to be reached by a stationary reference station.

 

[LittleBill21]

The little unit on a tripod is a portable reference station. Sometimes used for fields that aren't able to be reached by a stationary reference station.

so how is the portable reference station better? it doesn't know its exact location either, or is it generally a higher quality unit, that can provide better correction data?

 

[pmsmechanic]

I don't think it's better quality wise than a stationary reference tower. It's better because the tractor in the field can get signals from it vs the stationary tower that it can't get signals from. Most farmers around here have their own towers set up or pay a neighbor to use their tower. I don't see portable units much anymore.

Also the tower (portable or stationary) doesn't need to "know" where it is. The tractor triangulates it's position from a minimum of 2 satellites and a stationary tower and it knows where it is in relation to the tower and the satellites. That's all the tractor really needs to know to drive in a straight line.

Another fact to keep in mind is that the gps satellites etc. only send out signals. They do not receive signals from the earth. The tractor receives those signals and triangulates it's position from that information.

I don't 100% understand how it all works. What I do know from experience is that when it works it's great. When it doesn't work it's a pain in the rear. The tractor I drove all spring didn't have a working gps. So I relearned all the skills for driving straight that I developed in my 20's and got the spring work done. I call that skill eps. Ernie Peters steering.

 

[Torvy]

Cousins in the Black Hills use some of this tech. I watched them running the windrower that was equipped with GPS a couple of years ago. More accurate than the kid (25 ish) who had been working these same fields since he was 8 or 10. Once they set up, the operator is mostly just along for the ride. Monitors levels of drying agent and fuel and such.

It must be worth the expense. The ranch is run with scientific precision, but they also watch costs very tightly.

Anyone who hasn't seen a big family farm or ranch operation needs to try. It is truly amazing stuff.

 

[dodge man]

When I first started using GPS for land surveying we always had a second unit as a base station. This gives you accuracy of around one inch. We set the base up on a known point, which we set our own known points over the years but started from points set by the government over the years.

I never worried about different conditions between the base and the rover because it was fairly close, no more than a few miles away. A radio link connected the two.

Lately we tend to use an internet service to get corrections. We use a cell phone type link(a hot spot) to get the corrections. We pay for this service in Illinois and it’s through Trimble. Leica and Topcon also offer this. They have set up bases all over the state so you are using this network to work off. Obviously there is a lot of software and hardware development to make this happen.

As a rule different conditions between bases and rovers aren’t a problem, an exception might be you have heavy rain and storm over yourself and it’s small and isolated.

A little off topic but something that has improved gps is all the constellations. You have gps (United States), Galileo (European), Glonass(Russian) and Beidou(Chinese). When I first started using gps we had to do mission planning and maybe there was only about half the day there was enough satellites to work.

 

[SmallChange]

how is the reference station any more accurate, doesn't it suffer from the same ionospheric conditions?

The reference station does, but that doesn't matter. The fact that it is stationary and nearby means that the atmospheric errors will be almost exactly the same for both, and can be subtracted from the one you care about.

 

[dodge man]

One thing that I don’t know about ag users if they get indicators of the quality of the gps results. Our surveying equipment gave us indicators of the results and I always kept an eye on them. Even with the most modern equipment you still can’t get survey quality results in wooded areas.