ETL 1110-1-175
30 Jun 97
Figure 5-2. (Sheet 2 of 3)
density was high and kriging standard deviations
locations. Consequently, values of zero were used
were low. Kriging estimates were produced for the
for the nine new measurement locations and only
same grid and the basic univariate kriging estimate
the resultant map of kriging standard deviations
statistics are listed in Table 5-2 (water level B).
(Figure 5-3d) is of interest. The map shows that
The map shown in Figure 5-3c indicates that the
the kriging standard deviations in the lower left
ratio of the original kriging standard deviations and
corner, which formerly had values of about 0.8,
the kriging standard deviations with the nine mea-
have been decreased by a factor of approximately
sured locations removed is always very close to
0.25, which indicates that the kriging estimates,
1.00, which indicates that there is very little dif-
based on the geometry of the network, are more
ference between the two sets of kriging standard
reliable.
deviations and that water levels are oversampled in
the area where the nine measured locations were
5-3. Bedrock-Elevation Examples
removed.
i. To produce the second map (Figure 5-1c)
a. The following examples are for bedrock
nine locations were added in the southwest corner
elevations. The principal purposes of the examples
where the sampling density was relatively low and
are to familiarize the reader with a kriging exercise
the kriging standard deviation was relatively high.
using bedrock elevations and to describe block
In section 2-4, Equation 2-47 indicates that the
kriging. The data come from an area where bed-
universal kriging variance depends on the vario-
rock consists of a series of intercalated terrestrial
gram, the type of trend, and measurement loca-
deposits that have been weathered somewhat and
tions; in this respect the kriging standard deviation
then covered with alluvium. The opportunity for
does not depend on the values at measurement
measurement error in these types of data is
5-6
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