DGPS is used to achieve a sustainable improvement in the accuracy of GPS positioning.
The acronym stands for: “Differential Global Positioning System”. It involves a procedure which can substantially correct measurement errors in the GPS which have occurred as a result of various influences. Measurement accuracy of between one and three metres can generally be achieved. As a comparison: Normal GPS achieves an accuracy of between five and twelve metres, which is, of course, sufficient for most applications.
One doesn’t rely on one individual reception for the position measurement, but rather on two. One of these receivers is the “primary receiver” in the vehicle, while the other is a fixed installation “reference receiver”.
The position of the reference receiver is determined very precisely, for example by using alternative measurement methods or position averaging. When the reference receiver now receives its normal, inaccurate GPS position, it can ascertain the momentary size of the positioning error by means of comparison to the position previously measured precisely.
This deviation is now compared to the position ascertained by the primary receiver, and the actual position of the primary receiver is thereby ascertained. It goes something like this: At time t, the GPS was x metres off the mark in direction y; so, correct your position ascertained at time t by -x metres in direction y, and you will be spot on!
