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Modern Geomatics Technologies and Applications
observation instruments, in addition to advanced level of accuracy (Carosio
and Dupraz, 1993; Gikas and Sakellariou, 2008).
2. Monitoring of deformations
Earthfill/rockfill dams are subjected to different loads and external forces that
cause deformation of the structure, foundation and environment around them.
The most important forces are weight of dam body and reservoir pressure that
cause increase of stress in dam. Also, the weight of water in reservoir, change
of temperature and movements of the earth's crust are other factors that cause
deformation of dam. During the time, these factors result in the occurrence of
geometric (horizontal and vertical displacements of dam) or physical changes
(increase of stress in dam body). The geometrical and physical changes
should be controlled and measured to increase the safety, performance and
lifetime of the dam construction.
Safety monitoring of great dams is done by evaluation and control of a large
set of variables that describe the relationship between actions - such as
gravity, temperature, Hydrostatical pressure, etc. - and corresponding
structural reactions- such as stress, displacement, etc. - as well as the
properties of materials used in construction - concrete, embankment, and so
on. In this context, basic control variables are displacement of some discrete
points on the structure, foundation and surrounding lands of dam.
Generally, control methods for recognizing the movement could be divided
on two general groups: geodetic methods and non-geodetic (geotechnical)
methods. Geodetic techniques are divided to three groups: land surveying
methods, space methods based on satellite positioning (e.g. GNSS) and
