Main factors that affect the accuracy of GPS

Precision agriculture techniques are becoming increasingly widespread all over the world as more and more farmers are beginning to appreciate their cost-effectiveness and other benefits these methods can bring to a farm. GPS technology is one of the most essential pillars of precision agriculture methods, as it enables the use of tractor autosteer devices, field sensors, field drones, etc.

Naturally, the accuracy of GPS technology plays a huge role – the more accurate your GPS is, the better results you’re going to get on your farm. But if you want to ensure that you get the best level of GPS accuracy possible, it’s important to understand all the factors that influence it. Below, we will talk about 4 things that can change the accuracy of GPS devices:

Satellite position

GPS receivers use triangulation and satellite signals to accurately determine their position. While GPS receivers need to use signals only from 4 satellites to determine their location, if they are connected to a larger number of satellites, it can significantly improve their accuracy. For optimal performance, GPS receivers should see 4 and more satellites because the GPS receiver needs 4 satellites to work out your position in 3 dimensions. If only 3 satellites are available, the GPS receiver can get an approximate position by making the assumption that you are at mean sea level.

But the number of satellites is not the only factor that matters. To achieve the highest degree of accuracy, satellites also need to be spread out as much as possible. If a receiver is connected to a lot of satellites that are positioned close together, it won’t result in higher accuracy.

Recommendation: Buildings, trees, tunnels, mountains, clothing, and the human body can prevent GPS signals from the satellites from reaching a receiver. When possible, put your GPS receiver in a place where it has a clear and unobstructed view of a large portion of the sky.

Installation mistakes

If you want to achieve a high level of accuracy and avoid mistakes, you need to install your GPS device on the centerline of your machinery away from things that can obstruct the line of sight between the GPS antenna and the satellite. At the same time, the antenna shouldn’t be installed too high on the tractor if you are planning to work on steeply sloped fields. Here are some tips about the installation of a FieldBee receiver and RTK base station.
If you are going to use your own base station then you have to know that the mounting place should suit the following parameters:
    • flat surface;
    • above ground;
    • with open sky view;
    • away from the sources of electromagnetic radiation (generators, power lines, etc.);
    • far away from large metal constructions and high buildings;
    • in the centre of your fields with a max 25 km radius;
    • with WiFi access connected to the internet with enough signal strength.

GPS receiver quality and features

GPS receivers vary in the number of GNSS systems and frequency bands they can support. Devices that can support a larger range of frequencies and GNSS systems will be more accurate than the ones that can work with smaller ranges. For instance, FieldBee has created its RTK L2 receiver to provide higher accuracy for farmers who work on large fields and in areas that have a lot of hills, trees, power lines, and buildings that hinder L1 receivers.

Errors from interference with the environment

Since GPS antennas and satellites are located hundreds of kilometers away from each other, signals exchanged between them need to travel a long distance. This means that there are a lot of things that can distort those signals and cause subsequent errors in location determination. This can include changes in the GPS signal that occur in the thermosphere and troposphere, signal blockage and reflection due to trees, power lines, high buildings, highways, and other objects located close to the ground. All those disruptions of the signal are improved by L2 technology.

Final words

Things like GPS receiver quality and features, number and location of satellites, interference with different layers of the atmosphere and objects on the ground, and installation errors can significantly influence the accuracy of GPS devices. This is why it is so important to be very diligent and avoid making common mistakes when choosing a GPS system for your farm.
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