Some fundamentals оf DGPS

Today DGPS is often considered as magic tool to solve almost all problems in surveying and navigation. This is true for many applications. However, users might be disappointed by DGPS if they disregard fundamental principles of this technique.

DGPS is a real-time technique for kinematic point positioning which yields improved accuracies with respect to one (or more) reference stations. DGPS is based on the use of two (or more) receivers, where one (stationary) reference or base receiver is located at a known point and the position of the (mostly moving) remote or rover receiver is to be determined.

At least four common satellites must be tracked simultaneously at both sites. The known position of the reference receiver is used to calculate corrections in the observed (code or phase) pseudoranges. These corrections are then transmitted via telemetry to the roving receiver and allow the computation of the rover position with far more accuracy than for the absolute or single point positioning mode. The higher accuracy is based on the fact that GPS error sources are very similar over a distance of some hundred kilometers and are, therefore, virtually eliminated by the differential technique. An alternative to the above navigation mode is the surveillance mode where the remote receiver transmits the raw observation data to the base station where they are corrected and processed. This mode is sometimes denoted inverse DGPS.

Дата добавления: 2015-07-19