Developing Custom GIS Applications to Explore Digitally Vectorized Geologic Quadrangles

1
Developing Custom GIS Applications to Explore
Digitally Vectorized Geologic Quadrangles
Mark Graham, Dr. Andrew Wulff, Department of Geo
graphy and Geology, Western Kentucky University,
mark_at_geospace.co.uk
Geographic Information Systems (GIS) provide
powerful tools for the analysis of complex
spatial data. Digitally vectorized geological
data have been created by the Kentucky Geologic
Society (KGS) for the purpose of allowing spatial
analyses to be performed on geologic data. Use
of these digitally vectorized quadrangles require
a GIS software package. Although the widely-used
commercially available GIS software packages
offer a wide range of extremely powerful tools
for the visualization and analysis of geological
data, there is a steep learning curve associated
with their use, and the packages are not
universally available to those who may have needs
for such data. To make these vectorized geologi
c data more widely usable, a stand-alone, custom
GIS Geotutor has been developed based on a
tutorial (Ralston, 2001) using ESRI MapObjects
for Visual Basic (MOVB). Geotutor allows
digitally vectorized geologic data to be viewed,
and also utilizes powerful tools such as quantile
renderers, buffers, and intersects.
Although not designed to replace full-blown GIS
software packages, Geotutor will give geology
students, even in introductory level courses, the
ability to use complex geologic data and perform
intricate analysis without extensive training in
GIS. Geotutor can be used, for example, in
geology classrooms in high schools and
universities to enable students to learn geology
and GIS in a comfortable and friendly setting.
It can also be useful in interpretive display
settings to allow people, in parks or museums,
for example, to explore geological phenomena.
Terms Vector Digital vector data is com
prised of either points, lines, or polygons.
Digital quadrangles are a type of vector data as
they are comprised of polygons.
Raster Raster data are cell-based spatial data
sets. GeoTutor currently does not support
raster. However raster support is planned for
future versions of GeoTutor. Digital Map A map
that exists only as a computer file. Digital
maps can be comprised of vector and raster data.
Digital maps are highly versatile and can be
updated and altered in seconds.
Hard Copy Map A map that exists in some non-di
gital form (usually paper). Hard copy maps are
somewhat limited and cannot be easily edited.
Layer A collection of similar geographic featur
es.
The figure to the left diagrams the functionality
of GeoTutor. Despite the simple program
structure, the program retains tools that are
essential to view geologic data as well as the
functionality required to perform basic analysis
on spatial data.
The interface of GeoTutor (right) is designed to
be easy to use for beginners. This particularly
stands out when contrasted with the full
functionality of ESRIs ArcMap (far right).
2
Features can be selected from each layer.
Selected features can be buffered, saved as new
files, or intersected with other layers.
Information from the layers attribute table can
be displayed from the selected feature(s). In
this example, the X formation has been selected.
The attribute table displays rock code and the
area it covers.
Using GeoTutor for an Introductory Lab on
Geological Maps Starting map has all of the layer
s on a static display, similar to the information
on a typical paper/hard copy map
Using Geotutor, the student may choose to vi
ew just the surface elevations (typical
topography/contour map). Questions that may be
asked at this stage include identifying types of
drainages and using the Law of Vs to predict
direction of stream flow. Contour density is
easy to compare by using the Zoom feature.
At this stage, the student may add the surface
hydrology and compare predictions with actual
drainages and flow directions.
The student may choose to remove the surfa
ce hydrology and simply look at the bedrock
geology layer. Questions at this stage may focus
on the patterns of the contacts between
lithologic units, or floodplain and drainages.
By adding the surface hydrology to the bedrock
layer, the student may clearly see the
relationship between the two features. Students
can clearly discern that varying surface
hydrology elements reflect in the varying geology
or vice versa. At this stage, the student m
ay compare surface topography with bedrock
geology and answer questions about the
orientation of the beds. Students can determine a
given bedrock units strike and dip from
topographic and geologic data.
Multiple layers can be displayed at the same
time. Each layer can be symbolized in a unique
way. The order of layers can also be set. In
this example, contour lines are places on top of
a geology layer.
Geology can be symbolized in a variety of ways.
Unique values display features based on an
attribute value. For example, each rock type
could be drawn with a specific color. The
quantile renderer displays a series of symbols
whose colors change according to the value of a
particular attribute.
A buffer is a zone of specified distance around
features (ESRI, 2004). The buffer and overlay
tool will create a buffer and assign that buffer
values based on an overlay layer.
The intersect function will select features from
the current layer which intersect selected
features of a specified layer.
Geotutor was developed at the Western Kentucky
University GIS Research and development
laboratory and borrows heavily from tutorials in
Developing GIS Solutions with MapObjects and
Visual Basic (Ralston, 2001). The program is
still is the initial stages of development.
Future modifications will include a help menu, an
even simpler interface, and customized data
intended for use in geology classrooms.
Geologic quadrangles have only recently been
digitally vectorized in the Commonwealth of
Kentucky. GeoTutor makes use of these
quadrangles and other existing GIS data. In
order for the program to be a useful educational
tool in other regions, digitally vectorized
geologic quadrangles from other states and
specific classic geologic quads should be
integrated in the program.
Maps are not static. The user can zoom and pan
to explore geologic formations.
The zoom in feature causes the scale of the
map to get larger. The zoom out feature res
ults in the scale of the map becoming smaller.
The pan tool allows the user to move around th
e map without altering scale in order to
investigate different areas.
Acknowledgements Ralston (2001), Kevin Cary, Wes
tern Kentucky GIS Research and Development
Laboratory, Western Kentucky University
Department of Geography and Geology, ESRI, KGS.
References Ralston, B. (2001). Developing GIS So
lutions with MapObjects and Visual Basic. New
York OnWord Press. http//www.esri.com/software/
mapobjects/ http//www.uky.edu/KGS/