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GPS question update

N

notjustair

Well-known Member
The other day I posted about the tractor GPS changing course if the machine was left parked for more than a few minutes.

I called my sprayer and GPS guy and found out the deal. At least, here's the issue with my GPS. I bought a cheapo GPS ($1800) that uses the satellites for position only and doesn't do anything fancy like auto steer, talk with the planter, or talk with the sprayer controller. Once you buy it there aren't any subscriptions, etc.

This GPS (and maybe all) needs triangulation (two satellites) to determine location. When the tractor is not moving it goes down to one satellite and is not accurate. Thus the reason running it a pass would return the job to where it should be - the triangulation.
 
FWIW all GPS units require a minimum of 3 satellites to calculate a location fix in 2 dimensions. At least 4 satellites are required for a more accurate, 3 dimensional fix.
 
notjustair: All GPS systems need to triangulate to figure the position. The difference in cost is how many satellites, what satellites they read and how often they triangulate. Some satellites require a subscription for your GPS receiver to work with them. Is the "drift" your seeing when your stopped really an issue??? Also can you upgrade your unit with just additional programing or do you have to replace the entire unit???

I sold the JD Green star systems and the boys run Ag Leader. So I am not really well versed in what options you have. It also depends on how accurate of a system you want or need. The boys had to up grade several years ago because they wanted row shut offs on the planter and sprayer. That required a more accurate system then they already had. They did not have to get rid of their current system but just added to it.
 
Your "GPS guy" doesn't have an inkling as to how GPS actually works.

Imagine a circle on a map of the earth several thousand miles in diameter. With a single satellite, all your GPS receiver can tell you is that you're somewhere on that circle.

Now imagine two circles intersecting at two points. With two satellites the GPS knows you are at one of those two points.

The GPS needs at least three satellites to fix your position down to a single point. Each additional satellite improves the accuracy of its position fix.

High-end GPS receivers such as those used in agriculture use a variety of techniques to improve their accuracy. If your dealer doesn't understand terms like WAAS, WAD and RTK he doesn't understand the products he sells.
 
Sounds to me like an antenna issue. I use GPS for air navigation and the unit (if it doesn't have a remote antenna) needs a clear 360 deg 'view' of the sky. That means no roof over it. If it has this kind of view it should pick up 12 satellites easy. I presume you are not parking it in or next to a big building. The other thing is; when parked is the GPS turned off and all power removed from it? They have an internal battery that is necessary to "remember" where the satellites are supposed to be. If this battery goes dead it can take a heck of a long time for the GPS to "locate itself" each time it is turned on.
 
(quoted from post at 05:40:56 06/27/16) Sounds to me like an antenna issue. I use GPS for air navigation and the unit (if it doesn't have a remote antenna) needs a clear 360 deg 'view' of the sky. That means no roof over it. If it has this kind of view it should pick up 12 satellites easy. I presume you are not parking it in or next to a big building. The other thing is; when parked is the GPS turned off and all power removed from it? They have an internal battery that is necessary to "remember" where the satellites are supposed to be. If this battery goes dead it can take a heck of a long time for the GPS to "locate itself" each time it is turned on.
Click to expand...

That's interesting. My GPS in my Suburban has a roof over it and it and works fine.

Others have addressed the issues. Some have to do with quality of the unit, some the programing and others the number of sats the unit is currently communicating with. Outside factors can affect performance too. High end units can put you within a couple of inches on the ground while others a couple of football fields.


MarkB: Lot of folks sell stuff that they have no idea about. Look at some of the threads about auto parts. I wonder how many dealerships hired an expert to sell GPS units and some just handed their sales staff some literature and told them to read it.

Rick
 
Check out these two articles. Very good information.

<a href="http://www.farms.com/farmspages/expertsbio/tabid/293/default.aspx?newsid=18366&authorid=86">http://www.farms.com/farmspages/expertsbio/tabid/293/default.aspx?newsid=18366&authorid=86</a>

<a href="http://www.farms.com/farmspages/expertsbio/tabid/293/default.aspx?newsid=18629&authorid=86">http://www.farms.com/farmspages/expertsbio/tabid/293/default.aspx?newsid=18629&authorid=86</a>
 
Yes, you are correct in that a GPS can work fine with "some" roof over it however the more satellites it can "view" the more
accurate it gets. Some units are built to see all 12 where others are built to see fewer to start with and if, say, half are
blocked by the roof you start out at a disadvantage.
 
The guy I farm with switched from deere to agleader because of the POOR jd sf2 signal. It was as pricey as deere with ALL of the add ons. He is not sure if it was worth the money. I had agleader 2000 and 3000 in the past. They were behind with the software over the hardware. Their maping upgrades were expensive. Later when I traded computers, they would not give me an unloack code because I had not upgraded. I lost a lot of yield and tile maps because it was then outdated.

Deere will stiff you if your golbe goes down with sf2. You can't transfer it to the new globe. I guess we should hire the russian hackers.
 
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