referring to geological terminology standards in
Australia, digital geological map terminology
standards in the U.S., and Korean geological
dictionaries, and mapped Korean terms to the
corresponding English and Chinese terms for
Internet search. Besides, for geological terms, the
concepts and scopes of terms were defined by
specifying several data items. A total of 14
geological areas were defined including digital
geological informatics, ore deposits, geochemistry,
paleontology, geotechnology, geological process,
field mine terminology, geophysics, structural
geology, environmental geology, mineralogy,
lithology, historical geology, mathematical geology,
and geological GIS terminology. Particularly for the
area of digital geological map, this study analyzed
existing geological maps and then: first, extracted
objects by geological period necessary for digital
geological maps; second, extracted rock objects
distributed over digital geological maps; third, the
arranged rock unit adapted for Korean geological
maps into 6-stage classification items from the
broadest classification (sedimentary rocks, igneous
rocks and metamorphic rocks) to the most detailed
one referring to Australian thesaurus, lithological
classification (draft) in BGS(British Geological
Survey) and geological map unit classification in
USGS(United States Geological Survey); and fourth,
the assigned identification codes of geological age
and rock objects to the classification items. Through
this procedure, we made rock-time unit ontology
specification of digital geological maps. The digital
geological map classification system first divided
digital geological maps into spatial units and time
units. Spatial objects were extracted in rock units
composing geological maps for spatial units and in
geological time scale units for time units.
2.1 Extraction of Rock-Time Unit
Objects of Digital Geological Maps
The classification of minimum rock units of digital
geological maps aims at digitalization into
lithologically uniform minimum map units. The
minimum unit classification of digital geological
maps (proposal) targeted Korean geological maps,
and we selected a common 1:50,000 digital
geological maps as a material for analyzing rock
units. When the digital geological map was analyzed,
1961 rock facies objects were identified, and each
object was composed of rock, layer, stratum,
stratigraphy, age, geological structure, ore, the
chemical and physical properties of the rock,
geographical name, etc. These rock objects were
classified into rock units, and they were organized to
have atomicity from one another and to be in the
relation of spatial inclusion between superordinate
terms and subordinate stems. In this study,
‘minimum rock unit’ was used instead of ‘lithology’
for two reasons. One is that sediment, which is not a
rock but an unconsolidated layer, cannot be
classified lithologically in a strict sense, so we need
to classify rock units in a new way. The other is that
‘minimum unit’ means that objects on the same level
has indivisible atomicity.
2.2 Time Unit Classification of Digital
Geological Maps
Time unit classification of digital geological maps
used eon for broad classification, era for
intermediate classification, and period for narrow
classification. In the broad classification, time was
divided into the Precambrian Eon and the Cambrian
Eon, and the Cambrian Eon was again subdivided
into the Paleozoic Era, the Mesozoic Era and the
Cenozoic Era. Geological age identifiers used 4
upper-case alphabets for eons and eras and two
alphabets for periods. However, because the
Cambrian Period and the Carboniferous Period
overlapped with each other, they were given
identifiers CA and CB, respectively.
2.3 Rock Units Classification of Digital
Geological Maps
Rock units classification of digital geological maps
first made the broadest classification into
sedimentary rocks and unconsolidated sediments,
metamorphic rocks and igneous rocks, and then
broad, intermediate, narrow, detailed and most
detailed classification, so a total of 6 depths of
classification tree. Figure 1 shows a topic map of
major basic objects extracted from Korean digital
geological maps. Topic map is a methodology for
modeling a set of topics, organizing topics, relations
among topics, and resource information on topics
into ontology. A topic map is a technology standard
for defining knowledge structure in distributed
environment and mapping the defined structure to
knowledge resources. It is a new paradigm for
structuring, extracting and navigating information
resources. Terminology objects according to topic
marked as a box show Korean term, English term,
geological abbreviation and RGB color, and have a
classification identifier in subordinate classification
(Figure 1).
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