Leica Geosystems GPS Basics - Manual (Page 10)

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GPS Basics -1.0.0en How GPS works
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3. How GPS works
There are several different methods for
obtaining a position using GPS. The
method used depends on the accuracy
required by the user and the type of GPS
receiver available. Broadly speaking, the
techniques can be broken down into
three basic classes:
Autonomous Navigation using a single stand-alone receiver. Used by
hikers, ships that are far out at sea and the military. Position Accuracy is
better than 100m for civilian users and about 20m for military users.
Differentially corrected positioning. More commonly known
as DGPS, this gives an accuracy of between 0.5-5m. Used for
inshore marine navigation, GIS data acquisition, precision
farming etc.
Differential Phase position. Gives an accuracy of 0.5-20mm.
Used for many surveying tasks, machine control etc.