Leica GPS1200+, Техническое справочное руководство

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Instrument source The instrument source describes where the coordinate triplet was measured or entered. The
options are
GPS , TPS , LGO or Level .
Coordinate quality Description
The C oordinate Q uality is
• computed on the rover for code solutions and phase fixed solutions.
• an indicator for the quality of the observations.
• an indicator for the current satellite constellation.
• an indicator for different environmental conditions.
• derived such that there is at least a two third probability that the computed position devi-
ates from the true position by less than the CQ value.
• different from the standard deviation.
CQ versus standard deviation
The standard deviation as CQ would often be too optimistic. This is why the computation of
the CQ in is not simply based on the basic standard deviation algorithms.
For the standard deviation, there is, statistically, a 39.3 % probability in 2D that the computed
position deviates from the true position by less than the standard deviation. This is not
enough for a reliable quality indicator.
This is particularly true for low redundancy situations such as a constellation of four satellites.
In such a case the RMS converges to zero and the standard deviation would show an unre-
alistically small value.