Leica Geosystems GPS System 500 - Technical Reference Manual - Manual (Page 149)

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5. Configuring the Receiver Technical Reference Manual-4.0.0en
Height Smoothing and Filter techniques with kinematic GPS
Due to the nature of GPS, the height
is the weakest part in GPS measure-
ments. Height information can only
be received from satellites above the
antenna. Signals from the satellites
of the other half of the orbits are
blocked off by the earth.
Therefore, the GPS heights are less
“stabilised” than the positions where
information all around the horizon is
available. In kinematic surveys, this fact results
in height variations of a few centime-
ters as shown in the blue curve.
Some GPS monitoring applications,
however, require a stabilised height. By applying the filter, the height
variations are smoothed and most of
the noise in height component is
eliminated. In the diagram below,
smoothed heights are shown in red.