QUICKBIRD STEREO-PHOTOGRAMMETRY FOR GEOLOGICAL MAPPING
(CYRENE-LIBYA)
Riccardo Salvini ^ *, Marco Anselmi?, Andrea Rindinella® & Ivan Callegari *
* Center of Geotechnologies, via Vetri Vecchi, 34, San Giovanni Valdarno (AR), Italy
salvinir@unisi.it
KEY WORDS: Geology, Photogrammetry, Interpretation, Orthorectification, GPS, QuickBird, Stereoscopic
ABSTRACT:
QuickBird satellite image stereo-interpretation together with geological survey allowed the creation of geological and
geomorphological map at the scale of 1:10,000 of the Shahhat area (the old Cyrene, Libya).
Before interpretation, the satellite image underwent fusion between panchromatic and multispectral data; the orthorectification has
been performed by using the Rational Polynomial Coefficients together with the GCPs from DGPS measurements and the DEM
which has been created from the topographic map at the scale of 1:50,000.
From the QuickBird orthorectified image, a synthetic stereo scene was created by the introduction of an artificial parallax giving a
different relative shift in proportion of the terrain height. The geological and geomorphological maps have been created by the
restitution of the stereopair that has been oriented in digital photogrammetry.
1. INTRODUCTION Formation (Member of Shahhat Marl and Member of the Algal
Limestone, Abdulsamad, 2000).
The stratigraphic sequence ends with heterogeneous deposits
belonging to the Al Abraq Formation characterised by an
alternation of glauconitic sandstones, marly silts and shales.
The age of the sediments goes from 40 million of years at the
bottom up to 25 million of years at the top.
The activities carried out had the aim of evaluating the possible
correlations among geological and paleo-antrophic elements
supporting archeological diggings in the Ain Hofra area
(Shahhat, Libya), an important sanctuary that is actually topic
of study by the University of Chieti (Italy). For such work
modern and traditional methodologies of analysis, with the
purpose of getting detailed geological and geomorphological
data, were applied. In order to achieve the objective, the ;
analysis of the site has been carried out by means of detailed 7 Mediterranean Sea
geologic-geomorphologic survey, ancillary data, high resolution
remote sensed space data, differential GPS measurements and
digital photogrammetry of the whole Cyrene area.
2. STUDY AREA
The Shahhat area (the old Cyrene, Libya) is located in the
north-eastern side of the country, east of the Sidra Gulf nearby
the Mediterranean sea (Figure 1).
The Cyrenaica area is characterised by two relevant
morphologic escarpments, the upper dated to the Late Miocene
and the lower to the Thyrrenian (Middle-Late Pleistocene) that
are subordinate to the Al Jabal al Akhdar Mountains. The shape
and the structure of these escarpments, south-west north-east
oriented in the study area, are related to the tectonic and
geomorphological activity of the last 10-15 millions of years
(Carmignani et al., 1990). The elevation of the study area
ranges from 200 up to 700 meters o.s... The area is
geologically characterised by a monocline gently dipping
towards southward, sometimes crossed by transcurrent high
angle faults; from the lower to the upper part the lithologies
show quite a lot of variations: the lower part is made up by thin
limestone of the Darnah Formation (lower lithofacies) followed
by, on the top, marly and poorly marly limestone, rich in
macro-foraminifers (nummulites s.l), which are part of the
upper lithofacies; on the upper part thin levels of marly silts in
discordant contact, crop out overlapped by marly limestone
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Figure 1. Study area
3. MATERIALS AND METHODS
3.1 Available Data
The following data has been utilized for the execution of the
work:
- Panchromatic (Figure 2) and multispectral QuickBird
/ [ ilif aw Si. i J € d . ; . . +
very esiliferous (red SEaWGEd <1.} bélonging to the A Bay satellite imageries dated May, 7 2002 provided with the
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