Global Positioning System Reference
In-Depth Information
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[31
Lin
—
0.8
——
No
PgE
[31
Figure 8.6
Horizontal standard ellipses for GPS inner constraint solution and visibility
plot.
relevant quantities. Some of these plots indicate outliers (i.e., a deviation from an
otherwise systematic variation). These outliers are the prime candidates for in-depth
studies and analysis. Redundancy number and internal reliability plots appear useful
for identifying weak portions of the network (which may result from a deweighting
of observations during automated blunder detection). The variance-covariance matrix
of vector observations is the determining factor that shapes most of the functions.
The graphs below refer to the minimal constraint solutions only. Other aspects of the
solution are given in Leick and Emmons (1994).
A Priori Stochastic Information
The study begins with the variance-covariance
matrices of the estimated vectors from the phase processing step. A simple function
of the a priori statistics such as
k
1
+ σ
k
2
+ σ
k
3
σ
k
=
σ
(8.28)
is sufficient, where
k
identifies the vector. Other simple functions, such as the trace
of the variance-covariance matrix, can be used as well. The symbols on the right-
hand side of (8.28) denote the diagonal elements of the 3
×
3 variance-covariance
