International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
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Figure |. Geological setting of the Cappadocian Volcanic Province
(Toprak, 1998).
1.2 Data and Study Area
The study area is included within the Cappadocian Volcanic
Province between Ni&de and Aksaray (Fig. 2). It covers the
central portion of the province from Hasandag to Melendiz
Mountain, the 1:100.000 scaled map sections of L32, L33, M32
and M33.
The study area corresponds to a mountain belt that extends almost
in E-W direction. Total length of the area is 45 km and the width
is 30 km. The highest peak of the area is Hasandag with an
elevation of 3227 m. Average elevation of the plains surrounding
the belt is about 1000 m. The relief map clearly displays that the
Hasandag, Keciboyduran and Melendiz volcanic complexes have
very high topographic relief easily distinguished from the low
lying background.
Thematic Mapper (TM) images of Landsat 5 satellite are used
throughout the analysis. The area of interest is included within the
image 176/34.
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Figure 1. Location and topography map of the study area.
(Coordinates in black, are Universal Transverse Mercator (UTM) zone 36
coordinates with European 1950 datum; red ones are longitude and
latitude)
386
TM bands of 1,2,3,4,5 and 7 are used extensively in most of the
processes and the Thermal Infrared band of 6 is used only in a
color composite. The whole image having 2984 lines and 4320
columns of pixels is extracted to have a subscene of the study area
having 1172 lines and 1996 columns; in order to minimize the
disturbance of the unrelated pixels.
Furthermore, the volcanic units mapped in the area are separated
from the surrounding units to better highlight the intended output
maps. Geological map prepared by Toprak (1998) used as the
reference guide for masking out the non-volcanic units. The
boundary between the volcanics and fluvial deposits is drawn
manually as a polygon. The units outside this polygon are simply
cropped by using the TNT MIPS software.
The laboratory spectrum data for the minerals are gathered from
USGS spectral library. As there are many spectrum data available
for a specific mineral, the one which represents the other
spectrums tried to be selected.
1.3 Preprocessing
Geometric corrections are performed to eliminate the systematic
and non-systematic distortions related with the physical and
geometric conditions of the scanning devices. The remote sensor
data that is commercially available is already systematic error
removed, however non-systematic error remains in the image
(Jensen, 1996). The image data is accepted as free from geometric
errors.
TM bands 1,2 and 3 are correlated with the band 7 and the haze
amounts are decided. In the graph x-axis is the bandl and y-axis is
the band7 grey levels. Band 7 values start from very near to 0
whereas band 1 values start from 52, showing that the pixels are
displayed over-reflectant by this much, which known as a
radiometric error caused by the atmospheric transmission. Two
bands are highly correlated after the grey level of 52. This amount
is subtracted from the band 1 reflectance data to remove this error.
2. METHODOLOGY
During the analysis a simple to complex step-wise path is
followed. Each analysis result is compared with the previous one.
Conventional methods like color composites, several band
rationing techniques, principle components analysis (PCA) and
least squares fitting (multilinear regression) are applied to the
original unregistered raw data. Then the spectral library data used
to analyze the images by means of alteration minerals. The
resulting images are considered to be the potential alteration maps.
If the results display any convergence with the data acquired from
previous works then the final (combination) map of all techniques
is registered and processed and prepared for the ground truth. The
geology of the area is gathered from the published maps and
mostly forms the basis of the ground truth data. Lastly according
to the ground-truth study the applied techniques are criticized to
have the final conclusion (Fig. 3).
2.1 Conventional Analysis
Conventional analysis techniques include the image processing
techniques that are literally found to map the information
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