Calibrating DGPS
DGPS means "Differential Global Positioning System".
This system is used to determine the position of the vehicle.
When should you calibrate?
If and when you calibrate the signal is dependent on the signal you use:
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- If your GPS does not use a correction signal, you will need to calibrate the GPS signal every time before starting work.
- The more precisely you do this, the more precisely your system will operate. Conversely, the less precise the GPS calibration, the less precisely the system might be able to determine the position of the vehicle.
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- When using an RTK correction signal, you need neither set a reference point nor calibrate the GPS signal. The position of the tractor is continuously corrected by the RTK provider by means of a correction signal.
Problem description
Throughout the course of the day, the Earth rotates and the satellites change their position in the sky. The calculated position of a point will as a result shift. This shift means that the position will, after a certain time, no longer be up-to-date.
This phenomenon is called a "drift", and can be minimized.
For your purposes, this means that all of the field boundaries and guidance lines which you create during a day will have shifted after a few hours.
Solution to the problem
There are several ways to compensate for drift:
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- By using an RTK system.
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- Using the reference point – By setting the reference point and calibrating the GPS signal each time before starting work. A free option for farmers who work with EGNOS, WAAS or other DGPS signals that have a precision of approx. +/- 30cm.
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- It also briefly helps to shift the guidance lines.
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- By using a correction signal. A chargeable service provided by the GPS provider. Only for use in conjunction with a very accurate GPS receiver. The GPS signal must be re-calibrated automatically and at regular intervals.
Further information