Visual Analysis of Relevant Fields in Geoscientific Multifield Data - Towards an Interdisciplinary Approach in Earth System Science - page 211

Fig. 5 The field similarity
plot in the case of a single
time-varying field. Different
types of fields are clearly
separated. Individual views
for the highlighted points are
shown in Fig. 6

analysis on which alternatives work best for which application is beyond the scope
of this conceptual paper and left for future work.
In this paper, we normalized the range of each

field to the [0, 1] interval. In case
of noisy data, a distribution-based normalization method can be employed. It puts
the mean value of the distribution to 0 and standard deviations to ± 1. The latter

method is more robust against outliers.
Sammon

is mapping is a generally applicable projection method that produces
suitable results for many applications. However, our approach is not tied to this
particular technique, and other distance-based projection methods (Minghim et al.
2006 ; Paulovich and Minghim 2006 ; Paulovich et al. 2008 ) can be used.
The

'

field similarity plots in Sect. 5 were computed with the Euclidean distance
measure. In our experiments, we also employed a correlation-based distance
measure. In the multi

eld case, the correlation measure produced quite different
results. Here, the denser groups of original and derivative fields shown in Fig. 1

were widely spread, while the fields chosen for Fig. 3 were placed closer to each

other. The reason is that the correlation measure is less sensitive to the scaling of

fields with similar histograms but different spatial patterns are judged
to be more different. For the case of a single time-varying

fields. Thus,

field, the results produced
by the correlation-based measure were similar to those with the Euclidean distance,
only that the groups were overlapping and not so clearly separated.
From the purely information-based point of view, the common recommendation
to analyze the general behavior of the data is to take

fields that are spread in the
projected space and cover it well. However, it is clear that speci c targeted ques-

tions require inclusion of certain fields that capture the respective information.