SANDS Analysis Reveals Surface Oil in Gulf of Mexico
Dr. Sandy Ebersole, Geologic Survey of Alabama, sebersole@gsa.state.al.us
Dr. Sara Graves, University of Alabama in Huntsville, sgraves@itsc.uah.edu
OVERVIEW
The Sediment Analysis Network for Decision Support
(SANDS) project is utilizing enhancement methods to
highlight suspended sediment in remotely sensed data and
imagery of the Northern Gulf of Mexico. The analysis thus
far has shown that areas of suspended sediments can be
extracted from Landsat imagery. In addition, although not
an original goal of SANDS, the analysis techniques have
revealed oil floating on the water’s surface. Detection of
oil floating on the surface through remotely sensed
imagery can be helpful in identifying and understanding
the geographic distribution and movement of oil for
environmental concerns.
For more information: sands.itsc.uah.edu
Data from Landsat, MODIS and SeaWiFS were obtained from
NASA Earth Science Data Centers by the Information Technology
and Systems Center at the University of Alabama in Huntsville and
prepared for analysis by subsetting to the region of interest and
converting from HDF-EOS format (in the case of MODIS) to
GeoTiff. Analysts at the Geological Survey of Alabama (GSA)
working with Landsat data initially, employed enhancement
methods, including false color composites, spectral ratios, and
other spectral enhancements based on the mineral composition of
sediments, to combinations of visible and infrared bands of data.
Initial results of this approach revealed suspended sediments as
shown by Figure 1.
Figure 2. Landsat 5 image (path 21, row 39) of the eastern
Louisiana Delta and Chandeleur Islands on August 31, 2005
(2 days after Hurricane Katrina made landfall) in true color
(bands 1, 2 and 3).
Figure 3. The same area with preliminary spectral identification
of oil (yellow) floating at the surface
Figure 1. Southeasterly pointing wisps of suspended sediment
extracted from Landsat 5 imagery showing normal sediment transport
patterns east of Mobile Bay. These wisps correlate with sand ridges on
the seafloor.
The analysis technique also revealed areas of oil floating on the
surface of the Gulf near Chandeleur Island immediately after
Hurricane Katrina in 2005. Figure 2 shows a true color Landsat
image and Figure 3 shows the same image after enhancement. The
areas of floating oil are clearly visible. The oil washed out from oil
spills on land.
These results will be presented at the Geologic Society of
America in March, 2011
A. Tavis, S. Ebersole, J. Thorn, B. Brown, S. Graves, D.
Hardin, 2011, Suspended Sediment Analysis of Remotely
Sensed Gulf Coastal Imagery, Geological Society of
America Southeastern Section 60th Annual Meeting
Abstracts with Programs, Vol. 43, No. 2.
This work was performed under NASA contract NNX09AT46G