Measuring Volcano Symmetry Using SRTM Imagery

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Measuring Volcano Symmetry Using SRTM Imagery

• Hawkins, D. S., Mattioli, G. S., Jansma, P. E.

Arkansas Center for Space and Planetary Science,
University of Arkansas, 202 Old Museum Building,
Fayetteville, AR 72701. Department of
Geosciences, University of Arkansas, 113 Ozark
Hall, Fayetteville, AR 72701. Department of
Geography and Geology, Western Kentucky
University, 314 Environmental Science and
Technology Building, Bowling Green, KY 42101

• Introduction
• Volcano symmetries have been studied extensively
  by geologists, but currently there is no database
  of their symmetries. Typically, it is thought
  that shield volcanoes are more symmetrical than
  stratovolcanoes. This research will use SRTM
  elevation data to look at volcanoes on Earth to
  create such a database for future possible use
  for comparison with extraterrestrial volcanoes
  and to better understand the symmetry differences
  of various volcano types.
• Background
• The Shuttle Radar Topography Mission (SRTM) uses
  radar to develop a grayscale elevation model of
  the Earth.
• SRTM images are in one degree tiles at 90 meter
  resolution throughout the world and 30 meter
  resolution in the United States.

Figure 2. Color Enhanced Image of Volcan Cerro
Azul. Note the pixilation due to the 90 meter
resolution of the satellite. Ellipse is a
best-fit model of the volcano, with semi-major
and semi-minor axes marked in black and white,
respectively.
Figure 3. Spatial profiles of semi-major and
semi-minor axes of Volcan Cerro Azul, with
respective colors from Figure 2.

• Current Research
• Created a database of stratovolcanoes from the
  Chilean Andes.
• Began measuring North-South and East-West length
  and outlining volcanoes for batch-processing of
  semi-major and semi-minor axes.
• Created a database of approximately 150 shield
  volcanoes in the world.
• Future Work
• Finish current databases and process ellipses.
• Create databases for other stratovolcanoes in the
  world as well as cinder cones.
• Define a mathematical formula to quantify
  symmetry.

• Procedure
• Acquire SRTM data from NASA.
• Open SRTM images with ENVI software and enhance
  images using ENVIs prepackaged software.
• Measure North-South and East-West length of
  volcano using ENVIs measurement tools.
• Create an outline of volcano and apply a best-fit
  ellipse around the outline. Find the semi-major
  and semi-minor axes of the ellipse.
• Define a percentage of symmetry.

Figure 1. Raw SRTM Image of Volcan Cerro Azul,
Chilean Andes. Pixilation due to SRTM resolution.
Acknowledgements Herbert Pablo, Henry Turner,
Andrew Wulff