Trying to get my Head Wrapped Around This

As I mentioned before, on his birthday I believe, my ever brilliant husbands latest interest is farming with GPS. Or more accurately figuring out how to provide the GPS to farm with (or precision farming or site specific management or whatever). He is well down the path to getting it figured out and I am trying to follow him. So let me get it on paper, as such, so I can see how it works more easily.

It is kind of a chicken or the egg thing as to which comes first, the tractor or the base station, so I will start with the GPS satellites. They are in space streaming data down to tell us how to get places or tell us where we are. They talk to us. We don’t talk to them. That is important.

In order to use GPS for farming we need to know exactly where the tractor is. Down to the inch. So we have a base station, not in the tractor, and an antenna in the tractor. The position of the tractor is found by both tractor and base station receiving signals from the satellites. There are lots of satellites. American and Russian. They don’t rotate at the same speed as the earth so at times throughout the day many of them wont be visible which is why it is necessary to use the Russian satellites too.

The base uses the measurement of the distance, time, between it and the satellites and the tractor and the satellites to tell the location of the tractor. This is RTK, real time kinematic. (I feel kind of cool for knowing what that stands for like how I’m a real horse person because I know that a Coggins test is not for some disease called coggin but for Equine Infectious Anemia)

But we don’t talk to the satellites so how does the base station know where the tractor is to tell it where to go?

That’s where it gets complicated, cause it hasn’t been so far, so I’ll keep trying to figure it out. Until then here is a video that talks about it better than I can by the go to guy for this stuff.

Might be easier to watch here.