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Wednesday, May 8, 2019



Our ancestors had to go to extreme measures to keep from getting lost. They erected monumental landmarks, drafted detailed maps and learned to read the stars in the night sky. Things are much easier today, if you have a GPS receiver and a clear view of the sky, you'll never be lost again. 

The Global Positioning System (GPS) was developed in 1973 by a panel of United States Department of Defense scientists to help accurately define location using satellites as a reference. There are currently 31 US satellites in orbit of which 24 are active, the balance are spares that can be used as backups when one of the active satellites needs maintenance. These satellites revolve around the earth 6 times a day, so at any time there is 12 satellites on our side of the earth.  We need 4 satellites to generate an equation to pinpoint our location using a process called trilateration.  With trilateration our distance from each satellite is figured out based on the time it takes for the radio signal to reach our location from the satellite, with that information four circles are generated and the point at which they intersect is our location.

The GPS satellites send out multiple sets of information in its radio signal at various times.  One of the messages is the location of all of the satellites which helps in the trilateration process, but it only sends a portion of the info every few minutes, that is why it takes a while for accuracy to build on your receiver at a first start or a cold boot, it takes time to build up history of the satellite locations to improve your location. On a worm boot or RTK start up the receiver has history and shows greater accuracy quicker.

The former Soviet Union also has a satellite system known as Glonass, John Deere receivers use these satellites to improve our odds of receiving a satellite signal always. There are a few things that can affect our ability to receive a satellite signal thus affect our accuracy. Buildings, trees, leaves, power lines, solar flares, and the threat or reality of war.  These can all block signal or bounce the signal which is referred to as multipath.  Multipath can influence the accuracy by change the time it takes to receive the signal or generate multiple signals from the same satellite.  We have all seen the effects of tree lines or shading, luckily the occurrence of these is on decrease with better receivers, improved programing and history retention built into the newer receivers. 

Global Positioning Systems (GPS) have revolutionized farming. They’ve gone from an expense that couldn’t always be justified to a crucial part of many farming operations. John Deere guidance solutions are tailored to suit your operation and comfort level. They save you time, fuel and input costs with every pass on every acre. And, because efficiency increases with accuracy, John Deere enables you to easily upgrade from one guidance system to the next.  For more information of the full line of John Deere precision guidance products, contact your local R&S Integrated Solutions Consultant.  

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