Global Positioning System Reference
In-Depth Information
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accomplished through longer observation times, using dual-frequency receivers, and
processing with a precise ephemeris.
Internal Reliability
Internal reliability values are shown in Figure 8.13. These
values are a function of the internal reliability vector components as follows:
I
k
1
+
I
k
=
I
k
2
+
I
k
3
(8.31)
The internal reliability components are computed according to Equation (4.363) for
the decorrelated vector observations, and are then transformed back to the physical
observation space. The values plotted are based on the factor
4
.
12. There is
essentially a linear relationship between internal reliability and the quality of the
observations as expressed by
δ
0
=
σ
k
. The slope essentially equals
δ
0
. The outliers in
[31
Figure 8.13 are associated with small
σ
k
and pertain to a group of “single vectors”
that result when the other vectors to the same station have been deweighted. The
linear relationship makes it possible to identify the outliers for further inspection and
analysis. Furthermore, this linear relationship nicely confirms that internal reliability
is not a function of the shape of the GPS network.
Lin
—
1.5
——
Nor
PgE
Blunders and Absorption
Figure 8.14 shows blunders as predicted by the respec-
tive residuals. As detailed in (4.366), a relationship exists between computed blun-
ders, residuals, and redundancies. The figure shows the blunder function
B
k
1
+
=
B
k
2
+
B
k
3
B
k
(8.32)
[31
Figure 8.13
Internal reliability versus precision of baseline.
(Permission ASCE.)
