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The positioning method is dependant upon a single receiver station. This is also called 'stand-alone' GPS, because, dissimilar to differential positioning, ranging is effectuated strictly between the satellite and the receiver station, besides on a ground-based reference station that helps with the computation of correcting errors.
In this way, the position that is derived in without limit means are conditional to the unquestionable or unmitigated errors inherent in satellite positioning. The total accuracy of absolute positioning is regarded as no greater than 50 meters at best by Ackroyd and Lorimer and to be +100 meter accuracy by the U.S.Army Corps of Engineers.
Differential or Relative GPS takes the triangulation principles one -step ahead, with the help of second receiver at a familiar reference point. With a view to facilitate it ahead, determination of a point's position, as to the known earth surface point, this configuration enjoin collection of an error-correcting message from the reference receiver.
Differential-mode positioning reckon on an established control point. The reference station is situated at the control point, which is at a triangulated position; the control point makes the coordination there. In this way, the correction factor is permitted to be calculated and applied to other GPS units which are used in the very same area and in the very same series.
The inaccuracies that are kept in the control points coordinate are straightforwardly and literally constituent to errors inherent in the satellite positioning process. Error corrections taken by the reference station change rapidly, because the factors originating position errors are not static over time. This error correction gives allowance for an abundant amount of errors to be nullified, promisingly as much as 90 percent.
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