occurs at a certain distance from the central, most
uplifted part
of the Palmyrian ridges(from the El-Mrah,Abou
Rajmein and other anticlinal folds) towards the
Khasara and El-Mitlaa synclinal folds.
A study of the gravity field of the territory ( Fig 4)
shows that its gravity anomalies have in general the
negative values. Two zones, distinguished by different
characteristics of gravity fields are well defined on the
gravity map. These two fields are separated from each
other by a gravity interval of a North-Eastern strike the
intensity of which equals to 10 mgl. Spatially the
gravity interval coincides with a series of regional
folds, passing along the Southern face of the
Palmyrides.
A whole number of linear gravity anomalies of a
North-Eastern strike which practically coincides with
the strike of separate local structures of this area is
distinguished in the Northern half of the
territory(which unfortunatly has not been completely
covered by the gravity survey of the 1:500,000
scale). Towards the center of the El-Qayed and El-
Mazar anticlinal folds,the gravity anomalies change
from -35 mgl to -27.5 mg] and in the Tantour anticlinal
fold from -35mg] to -17.5 mgl. On the other hand,in
the Ad-Daww synclinat structure the values of gravity
anomalies change from -35 mgl in the sides to -50 mgl
in the center. The Southern and South-Eastern parts of
the surveyed territory are characterized by a relatively
undisturbed isometrical gravity field with a small
amplitude of variation of gravity anomalies - from -
27.5 mg] to - 42.5 mgl. Noteworthy is the fact that
spatially the chains of local gravity anomalies are
confined to the Al-Abtar and Sawwanet faults. In
conclusion, one should say with regard to the magnetic
and gravity maps that they confirm rather well the
division of the studied territory into two tectonic
regions which are marked not only by superficial
structural difference, but also differ substantially in
their deep structures.
Geologic Interpretation :
By using of Remote Sensing techniques, TM, Spot
imagery
shows three tectonical subzones, which can be
distinguished morphologically from south to north
(Fig.5). The first tectonical subzone includes major
anticlinal linear foldes, the second is characterized by
the series of linear box-shaped anticlinal foldes, the
third includes major structures situated north of the
Matnet System of faults. Remote Sensing techniques
helped to mapping the tectonical subzones, and gave
new information mainly in the plattform areas
surrounding the palmyrides.
A synoptic view of large areas is the major advantage
of using Satellite Remote-Sensing techniques. A
Landsat TM scene ( Fig.6) gave the same view as a
Landsat MSS-scene ( Fig.7), but TM's improved
geometric resolution makes it possible to detect objects
about one fifth the size of those detectable by MSS. As
most image-processing systems can display 512 x 512
pixels on a color monitor, this means that with MSS-
data with a pixel size of 80 x 80 m one can display an
area of 40 x 40 km, and with TM an area of 15 x 15
km. The conclusion from this is that an image-
processing system suitable for TM data should at least
be able to display 1024 x 1024 pixels on a color
monitor. Thus, one can also take full advantage of the
TM's high resolution and at the same time have the
same synoptic view of large areas as with Landsat
MSS. The linear features derived from SPOT scene
took roughly the same higher content of information of
the TM data(Fig.8). On the other hand, the resolution
offered by SPOT HRV imagery, plus the fact that SPOT
steriopairs are recorded directly in digital form, appears
to offer a more satisfactory approach to this type of
study. Reference to the the processing concepts, it is a
fact , that all information derived from TM-seven-
band sensor and Spot-three band-HRV sensor ,can not
conveniently be presented within one single image
product. Hence it is generally a problem to select a
subset from a multiband image for enhancement by
rationing , PC-analysis or color compositing. The
decisions on which strategy to choose are determined
by several different facts,involving the objectives of the
particular application, and the choice of bands and
algorithms. The enhancement of solely spectral
variations within two (or more) bands by
simultaneously suppressed albedo differences is the
major advantage of ratio trasformations. However,in
our data, non-linearities and non-periodic loss of rows
affects band to band registration throughout different
bands. Although haze-corrections were applied it was
not possible to remove the remaining patterns
completely. The principal component transformation is
a widely used method for calculating "n" new,
statistically independent components of "n" input
bands, based on the covariance matrix. It can be
applied to any number of bands. Three of the resulting
components may be displayed as a color composite, or
the components are used for decorrelation stretching
before retransformation. Based on correlation
techniques and known spectral characteristics, three
significant bands for additive color coding are selected.
The combination of bands 1,4,7(TM) facilitates
excellent overall rock discrimination. The digital
classification, though rendering more detailed
discrimination of the Palmyrides region than visual
interpretation alone, nevertheless represents only an
intermediary stage in the information extraction
process. The results of the digital classification have to
be reinterpreted and modified for the production of a
thematic map. The mapped lineaments from three test
areas were digitised and analysed, which have been
produced a variety of discrimination diagrams
including histograms, rose diagrams, sector maps and
gridded maps.
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
