You may never have thought about a
geologic map as a database before, however, the information contained on
a geologic map lends itself perfectly to cataloguing in database form.
What a geologist can see with the sweep of an eye, combined with reading
of a legend, can be transformed into a powerful digital data set.
In fact, once properly transformed, the computing power of a GIS engine
allows even more to be gleaned from a geologic map than that which readily
meets the eye.
The key to transforming a geologic
map into a database is having a data model that allows maximum flexibility
for querying the data and also rigorously follows the facts implicit in
the mapped relationships. Building the architecture of a successful
geological, map-related data base involves the basic understanding of geological
relationships that go in to making a geologic map, the implied relationships
that result from map patterns and some working knowledge of GIS engines,
requirements and querying language. In point of fact there is a remarkable
similarity to the logic that goes into capturing the topology (see below)
of a geologic map from the technical GIS standpoint, and the logic that
goes into making a geology map to begin with. In this regard, geologists
usually have a strong intuitive sense of how a geologic map database is
built; the processes of mapping and building a GIS are parallel ones.
This section outlines what we consider
to be the most critical parts of a geologic data model and some of its
implications and requirements for building, holding and interacting with
the data in digital form. The model is not unique to the digital format
or to two-dimensional representation although we limit ourselves to these
here. This is not meant to be an exhaustive list of what can be done with
such a dataset nor the advantages and disadvantages of using one, however,
given the acknowledged advantages of computers for rapid map production
and data manipulation, the advantages of a digital geologic database may
be more readily apparent once this model has been examined.
Strongly suggested reading: Chapters
1-4, Bonham-Carter, G.F., 1994, Geographic Information Systems for Geoscientists,
Pergamon, ISBN 0 08 042420 1. Most all of the examples in this book are
from minerals exploration.
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