International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
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Figure 8. The image shows in pink the high Biotite and low
Serpenite areas; in violet are drawn instead the low Biotite and
high Serpentinite areas. In order to make a first classification
check. we overlaid on the pink and the violet areas two vector
layers, which were drawn on the basis of the PNRA map. The
yellow vector layer shows the Biotite areas (GHGr), while the
green one, the Serpentinite areas (GHGa).
Looking at the fig. 8 vector and raster layer overlays, we think
that our first try to map the Antartica geological areas by means
of the Remote Sensing techniques has been useful. In fact the
realized classification seems to be in accord with the local
sampling drawn (PNRA map). This good result is visible in the
Mount Crummer area (Biotite GHGr areas, North-East of the
satellite scene). In this area is evident a good overlay between
the estimated Biotite concentration and the local sampling. The
South-East area of the image shows instead some bigger
problems. In this area in fact the shadows/light conditions of
some spots may have caused some errors in the CEM algorithm
classification.
In-the future, we intend to develop our method with the
following enhancements:
e The atmospheric and topographic correction of
the ASTER sensor scene (by the building of a
Digital Terrain Model of the study area. These
corrections should help to solve under and over
lighting problems of the raw data.
e Operate a more accurate classification of the rock
outcrops in the ASTER sensor scene. In fact the
PNRA map has been drawn on the basis of
summer samplings while the satellite scene is
dated November, a local very cold period. This
fact has surely caused a different ice cover in the
two different maps.
After the said corrections we will verify the rock classification
on the basis of automated procedures that can count the pixel
numbers in the PNRA map and in the classified satellite image.
At last we will analyse the study area with a different year
satellite image in order to point out some possible icy cover
changes and, in this way, make a better rock outcrop
classification.
Notes
(1) Terra satellite has been launched in December 1999 by
NASA within the framework of EOS project (Earth Observing
System). It carries the following instruments: ASTER
(Advanced Spaceborne Thermal Emission and Reflection
Radiometer);
CERES (Clouds and the Earth's Radiant Energy System); MISR
(Multi-angle Imaging Spectro-Radiometer);
MODIS (Moderate-resolution Imaging Spectroradiometer);
MOPITT (Measurements of Pollution in the Troposphere).
ASTER acquire high resolution Earth images (pixel from 15 to
90) in 14 different bands of electro-magnetic spectrum, from
visible to thermal infrared (Abrams et al. 2003). In the scientific
community, ASTER images can be considered a very
innovative tool to obtain detailed maps of land surface
temperature, emissivity, reflectance and elevation.
(2) The JPL Spectral Library includes laboratory reflectance
spectra of 160 minerals in digital form. Data for 135 of the
minerals are presented at three different grain sizes: 125-
500um, 45-125um, and <45um.
(3) The Constrained Energy Minimization (CEM) algorithm
attempts to maximize the response of
a target spectrum and suppress the response of the unknown
background signature(s). It is appropriate to the situation where
the sought material is a minor component of the scene. It is
optimal for detection of distributed subpixel targets such as
mineral occurrences or sparse vegetation (ERDAS, 2002).
(4) Calculated abundance values can be negative or greater than
one. The negative values are a result of statistical variations
around the assumption of distributed noise with a zero mean
(maybe connected to the atmospheric scattering or to under/over
lighting conditions due to the land morphology). Abundances
greater than one can result if the input target spectrum is not
entirely pure or of exactly the same composition as pixels
within the image (ERDAS, 2002).
(5) Matrix analysis produces a thematic layer that contains a
separate class for every coincidence of classes in two layers. In
other words, it gives all the possible combinations of the classes
of the thematic layers (3 classes for the Biotite and 3 classes for
the Serpentinite = 9 classes in the matrix layer).
5. References
Abrams M., Hook S., Ramachandram B., ASTER User
Handbook, Jet Propulsion Laboratory, Pasadena CA, EROS
Data Center, Sioux Falls SD, 2003.
Capponi G., Crespini L., Mecchieri M., Musumeci G., Pertusati
P.C, Relief Inlet Quadrangole (Victoria Land) — Antartic
Geological 1:250.000 Map Series; PNRA (Programma
Nazionale di Ricerche in Antartide), University of Siena, 1999.
Elliot, D. H., Tectonics of Antartica — A review, Am. J. Sci,
275°, 45-106, 1975.
ERDAS, Imagine Spectral Analysis User's Guide, Erdas Inc.
Leoca Geosystem, GIS & Mapping Division, Atlanta, 2002.
Fitzgerald, P. G., The Transantarctic Mountains of Southern
Victoria Land: the application of apatite fission track analysis
to a rift shoulder uplift, Tectonics, 11, 634-662,1992.
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