Cory L. Walker '15, Computer Science at Washington and Lee University
Abstract: Monitoring changes in coral reefs can be accomplished by taking multiple images of designated areas
of the reef each year and quantitatively comparing live coral abundance from year to year. To determine
percent live coral per meter square, we manually segmented all live coral cover in photographs of m2 quadrats
using the pen tool function in Adobe Illustrator. Percent live coral cover was then calculated using
MATLAB. This method is very time-intensive and can take over one hour per image, depending on the
density of living coral. In order to better understand how the coral reefs are changing over time, we
need to speed up this process so that more time can be allotted to collecting and analyzing data. Here
we present a MATLAB program that provides a semi-automatic method for segmenting live coral with
only a few clicks. In our alpha test, we used both the manual and semi-automatic methods on 10 typical
quadrats. For each quadrat we obtain 5 segmentations: two independent manual segmentations, one
collaborative manual segmentation that we consider ground truth, and two independent semi-automatic
results. In evaluating our method, we found that manual segmentations average a 2.5% discrepancy in
estimated live coral coverage, while our method averaged 2.0% discrepancy. Additionally our semi-
automatic method averaged a 5.7% discrepancy with manual results, with a median of 3.15%. We look
to improve our program on two fronts, both to reduce discrepancy with manual raters and to improve
efficiency. With these improvements we can spend more time obtaining data and monitoring changes in
coral reefs.
pdf of the poster
GSA Proceedings website