Interi
SATELLITE IMAGERY ELABORATION (ASTER SENSOR, TERRA SATELLITE),
IN ORDER TO MAP ROCK DISTRIBUTION IN EXTREME AREAS. THE PRINCE
ALBERT MOUNTAIN CHAIN (VICTORIA LAND - ANTARTICA).
A. Favretto* R. Geletti**
*Dept. Of Geographical and Historical Sciences University of Trieste (Italy) andrea.favretto(@dsgs.univ.trieste.it
***[stituto nazionale di Oceanografia e Geofisica sperimentale Trieste (Italy) ricletti@@ogs.it
KEY WORDS: Geology, Identification, Global Environmental Databases, Satellite, Thematic, Method.
ABSTRACT.
The present paper is a first attempt to use Remote Sensing and GIS methodologies in order to draw a rock distribution map in
a extreme land as Antarctica.
To this aim we elaborated an ASTER sensor image (Terra satellite). This sensor records medium resolution satellite images
(from 15 m to 90 m pixels) in 14 different bands (from visible to thermal infrared). In the scientific community ASTER data
represent a new tool in order to create land use maps, thermal distribution maps and 3d models of the territory.
The adopted methodology is applied to a training area in Prince Albert mountain chain (Trans Antarctica Ridge — Victoria
Land - Antarctica).
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We checked the spectral response of the satellite image pixels; then we estimated the kind of rock by the presence of different
minerals in it. We did this comparing the reflectance values of the satellite image pixels with the one recorded in laboratory on
each mineral in the different wavelengths corresponding to the ASTER sensor 14 bands.
In order to control our estimation, we used a geologic map of the same area. This one was drawn within the framework of the
Italian National Research Program in Antarctica (PNRA).
We choose a ASTER sensor satellite scene recorded in the period
of maximum ice cover on the land, in order to grant a
minimum outcrop in the case of an eventual manual check in Antarctica.
1. Introduction
This work is aimed at developing a methodology to allow the
mapping of extreme geographical areas like Antarctica. The
methodology consists of using remote sensing combined with
GIS techniques and has been developed in order to support
traditional in situ field survey techniques.
The Antarctic continent is a deserted and remote landmass,
almost entirely covered with ice. It has a complex geological
history, which has not yet been fully understood or rebuild and
it is still in evolution. Since ice occupies more than 98% of the
entire continent, fieldwork and surveys involving traditional
methods of investigation by direct observation of outcrops or
sediments is possible only in a few areas: where the ice is
absent, along mountain chains or on top of isolated peaks and
under the peri-Antarctic seas. Our work shows how combining
information obtained by remote sensing with the ones given by
direct outcrop observation can improve the geological history
knowledge of the Antarctic continent. The study area is located
in the Prince Albert mountain chain which belongs to the
Transantarctic Mountains (TM). TM lie on the cost of the
Victoria Land (VL), western Ross Sea, and they extend for
more than 4500 km, reaching an altitude of about 4000 m. The
TM are one of the world’s best examples of rift shoulders
(Stern, Brink, 1989; Fitzgerald, 1992). Geological information
about the extension of the West Ross Sea region comes
primarily from fieldwork carried out along the TM. The study
area is characterized by outcrops of Precambrian—Paleozoic
crystalline (granitic) basement and Jurassic volcanic sills (Gunn,
Warren, 1962; Elliot, 1975). This area has been chosen as it
presents the best conditions for this study, having a good
coverage of mapped outcrops (Capponi et al., 1999), and thus
allowing us to verify the results obtained from application of the
methodology we propose.
The methodology has been tested on an image obtained from
the satellite Terra, ASTER sensor (1) dated 1/1 1/2000. The
image has been acquired during the Antarctic winter in order to
have the most ice sheet coverage. This fact allows us to study
the outcrop and thus, to test the methodology in the worst ice
conditions. The methodology consists of comparing the pixel
spectral responses of the studied satellite image acquired by
ASTER at different bandwidths with the reflectance values
obtained from different wavelengths recorded on the mineral in
laboratory. Two different rock types have been identified and
mapped. The results have been compared with the geological
map of the area (Capponi et al., 1999) compiled in the context
of the Programma Nazionale di Ricerche in Antartide (PNRA).
This comparison allowed a first testing of the used
methodology.
2. Database
We used the following data:
e An ASTER sensor scene (Terra satellite), dated
1/11/2000;
e A geological map: Relief Inlet Quadrangole (Victoria
Land), 1:250.000 scale.
All data elaboration have been made with Erdas Immagine 8.6
and Esri Arc Gis 8.2
3. Data elaboration
We first transformed the PNRA geologic map in a digital form.
The digital map has been then rectified in the Polar
Stereographic coordinate system (WGS 84 spheroid ). With à
subset procedure we isolated the study area (Prince Albert
Mountain, area around the Larsen Glacier, fig. |).
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