A OPEN PIT MINING AÇIK OCAK MADENCİLİĞİ

23 rd
Assessment of Landscape by Photogrammetry Proximity Uav
Survey Technique: A Case Study of an Abandoned Mine Site in
the Furtei Area (Sardinia-Italy)
S. Cara, M. Fiori, C. Matzuzzi
Consiglio Nazionale delle Ricerche – IGAG-UOS di Cagliari, Cagliari, Italy
ABSTRACT In the past open pit excavations often created risks and environmental impacts
derived by the mining activities that deeply changed the landscape. In South Sardinia the
Furtei area, at Monte Porceddu, is a typical example of kaolinitic clays open pit mine, where
exploitation activities have deeply altered the original landforms. After mining closure this
site was totally abandoned and represents an extremely dangerous place. Nowadays the
possibility to recovering this site depends on the knowledge of local geolithological asset and
the hydrological characteristics of the sub-surface drainages. In this paper we present a
method based on a detailed photogrammetric UAV survey to generate multiple high quality
dense digital surface models (DDSMs) in order to provide basic terrain analysis. The
photogrammetric UAV method allows to survey risky areas with reliability, accuracy and
safety and, after some post-elaboration procedures, to point out complex geometric surfaces
characteristics related to geological and hydrological informations.
1 INTRODUCTION
In the rehabilitation of abandoned mining
areas the final result is mainly conditioned
by a consistent reconstruction based on the
accurate measurement of the morphological
alteration of the post-mining landscapes.
The success of a rehabilitation program
depends on the understanding of the new
geomorphological and hydrological asset as
well as the erosion processes derived from
post-mining activities. Digital surface
models of landscapes are more and more
used to reconstruct and evaluate this
degradation processes, particularly for the
risk assessment of a landform design (Fadda
et al. 2010). High quality digital elevation
model of a mining site was created with a
UAV multirotor platform photogrammetry
system. The aim of our research is to
describe the erosion processes caused as a
result of the abandonment of the mining
area. We mainly focused our survey on the
quarry vertical walls and on landfill mining
tailings, creating digital high resolution
georeferenced digital surface models
(DSMs) and digital elevation models
(DEMs). Due to the variability of surfaces
morphometry, in this case has not been
possible to define a unique DSMs resolution
that could be applied to the whole area.
Therefore the resolution of the DSMs,
compared to the average size of the drainage
network, was designed to enable the
representation of the smaller process, on the
basis of the minimum pixel dimension.
This method reduces the approximation of
digital models due to interpolation errors,
especially in presence of strong steepness,
giving a more detailed DSMs. The more
detailed models highlight the degradation
processes taking place on the surfaces that
otherwise could not be properly identified
and quantified. This DSMs allow to study
not only the erosion of the mining area,
obtained on the basis of tools such as terrain
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