This work reports the development of a system for fast and accurate determination of astronomical latitude (Φ), longitude (Λ) and azimuth (A). The system consists of a high-precision total station, with the appropriate software for automatic registration of the measured elements, connected to a GPS receiver through which accurate UTC timing is provided. This system allows the acquisition of a large amount of data during the tracking of selected stars around their meridian transit. After the appropriate processing of the data, an accuracy of σΦ = σΛ = ±0″.01, σΑ = ±0″.2 may be achieved for the determination of the astronomical coordinates and azimuth.The developed system compares favourably to older classical ones, due to its compactness and the accuracy obtained within a short period of time. Thus, combined with GPS receivers for the geodetic coordinates determination, it can easily be used for the determination of the deviation of the vertical and eventually of the geoid separation N.

This work, related to the activities of the CERGOP Study Group Geodynamics of the Balkan Peninsula, presents a method for the determination of the variations ΔN and, indirectly, of the geoidal undulation N with an accuracy of a few millimeters. It is based on the determination of the components ξ, η of the deviation of the vertical using modern geodetic instruments (digital total station and GPS receiver).

An analysis of the method is given. Accuracy of the order of 0.01arcsec in the estimated values of the astronomical coordinates Φ and Λ is achieved.

The result of applying the proposed method in an area around Athens is presented. In this test application, a system is used which takes advantage of the capabilities of modern geodetic instruments. The GPS receiver permits the determination of the geodetic coordinates in a chosen reference system and, in addition, provides accurate time information. The astronomical observations are performed through a digital total station with electronic registering of angles and time.

The required accuracy of the values of the coordinates is achieved in about four hours of fieldwork. In addition, the instrumentation is lightweight, easily transportable and can be setup in the field very quickly. Combined with a stream-lined data reduction procedure and the use of up-to-date astronomic data, the values of the components ξ , η of the deviation of the vertical and, eventually, the changes ΔN of the geoidal undulations are determined easily and accurately.

In conclusion, this work demonstrates that it is quite feasible to create an accurate map of the geoid undulation, especially in areas that present large geoid variations and other methods are not capable to give accurate and reliable results.

This work deals with the establishment of a close–range standard 3-dimensional geodetic network in order to certify the GPS receivers’ proper function. The standard network is located at the area of the University Campus of NTUA at Zografos Athens, Greece.

The first aim is the determination of the X and Y coordinates and the orthometric height H of the network’s points as well as the determination of their uncertainties by accurate terrestrial measurements.

The final target is to check any pair of GPS receivers.

The above standard network consists of five points, marked by special pillars, which ensure the stability of their place and the single setting of both a Total Station and a GPS receiver.

The terrestrial observations consist of horizontal and vertical angles and distance measurements between the points. The measurements were carried out by using a digital total station Leica TCA 1800 and the indispensable and appropriate accessories such as tribraches, prisms, targets, heavy forced centering bases, prism holders and adapters, which lead to the maximum possible measuring accuracy.

The adjustment of the terrestrial measured data was carried out in the Greek Geodetic Reference System 1987 (GGRS ′87) by the least square method.

The standard network was used in order to check a pair of GPS receivers Trimble 4600LS. Ten baselines were measured and determined the coordinates of the five points and the corresponding uncertainties in the same reference system.

The comparison of the measured elements such as distances, horizontal angles and height differences as well as the calculated coordinates of both solutions, leads with credibility to the certification of the proper or improper function of GPS receivers and to the checking of their industrial prescribed accuracy.

This work presents a method for the thorough research of the orientation of monuments, based on state-of-the-art geodetic and astronomical measurements. These measurements permit the production of an astronomically oriented, digital plan of the monument, a digital diagram of the perceptible horizon around the monument and a digital reconstruction of the apparent path of the Sun, as it rises above the horizon at characteristic dates. The data reduction procedures are rigorous and lead to an accurate determination of the orientation of the monument. The orientation is then interpreted in terms of other, mostly cultural, information about the scope of the monument and its time of construction. In retrospect, therefore, the method provides an independent determination of the time of construction of the monument within a narrow chronological range. The effectiveness and accuracy of the method is demonstrated by its application to the late Byzantine church of the “Assumption of Virgin Mary” in the Greek town of Kalabaka. The orientation of the main axis of the church is geometrically determined to an accuracy of 0.6 arcminutes. Combining all geometric data with cultural and historical information, we determine the time of construction of the church (1000 AD ± 13 years).

The exact foundation date of many early Christian churches is still unknown or according to archaeologists’ estimation it is attributed to a large time interval. According to a new astrogeodetic methodology, today it is feasible to assess it. This paper deals with the determination of the orientation, the foundation date and the dedication of nine Early Christian basilicas, situated in Central Greece. According to the suggested methodology, the appropriate geodetic and astrogeodetic measurements were carried out on the site of each Early Christian basilica in order to: Determine the accurate position on the surface of the earth by the calculation of its coordinates, Draw the accurate digital plan, Define the basic longitudinal axis, Calculate the astronomical azimuth of the basic axis via observations to Polaris (· Ursa Minoris), Create the profile of the perceptible horizon, Determine the apparent transit of the Sun for different dates. Combining all the above data for each Early Christian Basilica, the total geometric documentation of the monument was made. The detection of its foundation date and its dedication were achieved with adequate precision and reliability. Last, their selectable and systematical astronomical orientations were registered and a data base including all the above data had been created.

The determination of the astronomical azimuth of a line is not a difficult task for surveyors any more. The aim of this paper is to analyze the theoretical details and errors in order to propose the use of ordinary total stations, for an easy, efficient and accurate determination of the astronomical azimuth of a line by the hour angle method via Polaris sightings. As many modern total stations have a built – in quartz clock they can register automatically the UTC time as well as the angle measurements (horizontal and zenith) of each observation. The total fieldwork time needed is about 10 minutes and the accuracy that may be achieved is about ± 2″. This procedure will be proven to be easier than the determination of the geodetic azimuth of the same line. The calculation is independent and the result is free of the errors that the coordinates of a survey mark may contain, because they are not used. However good positional data is required from other sources. Astronomical azimuths are an alternative solution for the surveyors in order to check or orient their field surveys and arbitrary networks independent of the GPS system.

Apollo’s sacred island, Delos, is an extended archaeological site, which contains important monuments dating from prehistoric to Hellenistic times. In this article the orientation of some of the most significant monuments of the site are studied.

Each monument has been measured by means of modern accurate geodetic and astrogeodetic methods and instrumentation so that its plan, its main (longitudinal) axis, the profile of the perceptible horizon as seen from the monument and the astronomical azimuth of the main axis are determined.

Special attention and study have been reserved to the Cave of Kynthos (Andron), as the latter was considered as an ancient observatory.

This study attempts also a possible dating of the measured monuments based on their orientation and its relation to special celestial bodies.

All data deduced by measurements and calculations, as well as historical information have been used for the creation of a database in Macromedia software.

This paper investigates the orientation of eleven mosques situated in several regions of Greece. The aim of this work is to verify whether and how accurately the monuments have been constructed according to the Muslim tradition. As geodetic and astrogeodetic methods are used, the geometric documentation of each monument is carried out and its astronomical orientation is determined. The qibla for each monument is calculated by using geodetic equations. The mosques’ main axis azimuths are determined by a precision of some arc minutes. Also, their orientation, relative to the Canopus star (Alpha Carinae)—which the tradition has closely related to Kaabah in Mecca—is examined. All the mosques seem to follow the religious rule.

Reflectorless distance measurement provides the ability to easily make quick measurements saving time and labor for surveyors. The precision and accuracy of these types of measurements are under discussion because of the variety of parameters that can affect these measurements that are not well-understood. This paper attempts to answer some of the questions that have arisen about the credibility of reflectorless distance measurements ranging up to 50 m. An experiment was carried out using 26 different materials as the reflecting surface (these materials were also of differing colors). Additionally, the experiment used three different angles of incidence of the incoming electromagnetic energy with three different types of reflectorless total stations over a variety of ranges. A further experiment was conducted with an additional total station using 11 different materials at different ranges. To properly evaluate the results, a special supporting base was manufactured for holding the reflecting surface to ensure accuracy in the evaluation. The results are presented in tables and the conclusions that are derived indicate that further investigation is needed, especially at longer distances, as the parameters that influence reflectorless distance measurement in those situations are many more, and more important than at short ranges.

In order to monitor the deformations of modern constructions a local 3D network was usually being established at the surrounding area. The centering error, of both the instrument and targets, causes significant uncertainties in the determination of the x, y, z coordinates of the network’s points. In order to assure precise centering for both the instrument and targets, not only for the accessible but also for the inaccessible network’s points, a prototype way of marking is being implied. A special semi-permanent portable metallic stand (photo 1) was manufactured for marking the accessible points. The stand provides forced instrument centering of the order of ±0.1mm. It is light enough to carry, it accelerates and facilitates the centering and leveling of the instrument as well as it eliminates the time needed for the measurements. The applied laboratory checks in order to certify the suitability of its use and the provided accuracy are being described. For the inaccessible points special targets were used. The targets were put in permanent attachments (photo 7), (photo 8), which were also manufactured. Useful conclusions were drawn when these special accessories were used in to a 3D network, which was established for the monitoring of a new football stadium. Two measurement phases were carried out. The first one with the stadium being empty and the second one when it was crowded (about 32000 people) during a significant football match.

Geodesy can make a significant contribution to the monitoring of structures. The geodetic methods that have been developed can give reliable results. The aim of this article is to use the results obtained through the monitoring of a structure to predict its position in the future, using ANNs. Itpresents a detailed study on the development of an ANN that can be used to predict vertical displacements in a cultural heritage monument, with the ultimate aim of preventing it from falling apart. To this end, a geodetic network of 15 control points was established. The results of twelve series of geodetic measurements and adjustments to this network are used in this study. Using the trained ANN, the vertical displacement (ΔΗ)of any specific point in the monument’sgeodetic network can be predictedfora certain time in the future, with an uncertainty of ±0.5mm

This paper presents the integrate procedure for the documentation and fabrication of the 3D Digital Terrestrial Model (DTM) of inaccessible and rough surfaces. The proposed procedure combines the use of modern Image Assisted Total Stations (IATS) with Rapid Prototyping (RP) Technology. The determination of the measurement accuracy, as well as, the a-priori estimation of σo of the surface creation is achieved by using the Monte Carlo technique and the least square method. Also, basic concepts and principles of RP technologies are presented. The application of the procedure was realized at the difficult and inhospitable area of the central crater “Stefanos” on Nisyros Island’s Volcano, Greece. The a-priori calculation of the minimum essential scanning step, as well as, the testing use of two IATSs is included. Additionally, the elaboration and the special algorithms used for the actual RP fabrication of the crater’s tangible model are illustrated. Finally a scholastic check of the model’s reliability is applied.

The planned astronomical orientation and positioning of all kinds of monuments was proved by numerous investigations all over the world since the 19th century. Some cult, social or utilitarian purposes dictate a concrete orientation for each one. In this paper are being determined the individual orientation and the dating of Parthenon and He-phaisteion as well as a strong relationship between these significant monuments of the classical era is emerged. The exceptional symmetric placing of these monuments, as proved by this research, in ancient Athens is truly remarkable. Thus the strong religious relationship between the temples is also geometrically documented. The modern instru-mentation used today and the special developed astrogeodetic methodology permit the accurate (some arc seconds) determination of a monument’s orientation. Additionally this fact may be also a long discussion between archaeologists, archaeoastronomers and humanists.

Each level and its accompanying rods constitute an integral levelling system. The check of a levelling system is essential in order to ensure the credibility of the geodetic applications where is used. A convenient and cost effective methodology for checking levelling systems is presented through this work. The methodology is based on a low cost innovate comparator which constitutes the basic tool. Using this comparator the levelling systems, which provide accuracy minor or equal to ±1mm/Km, can be checked within 30 minutes. The process, which should be followed as well as the applied statistical tests are analyzed. These tests respond both for the proper operation of the system and the achievement of its nominal accuracy. Additionally the manufacture of the comparator as well as the selection of the used materials is presented. Moreover the calibration methodology of the comparator is described in detail. Finally the results of four levelling systems that were checked are evaluated. It is proved that both tests are necessary as there are cases that a levelling system achieves the nominal accuracy although it doesn’t operate properly due to a systematic error. So, useful conclusions are elicited about the convenience and the use of the methodology.

The increased use of GNSS for technical constructions and infrastructure works makes necessary the calculation of local accurate geoid undulation’s models for the determination of accurate orthometric heights. Apart from the conventional methods, artificial neural networks (ANN) are also used for this purpose. Specially, back propagation artificial neural networks (BPANN) are widely applied for engineering practice. It is well known that the training of ANNs consists a "black box", as the user cannot interlope in the procedure. The aim of this work is to investigate the impact of some crucial parameters to the accuracy, of geoid undulations determination, when BPANN is used. Parameters as the different types of input data (ellipsoidal or Cartesian coordinates, ellipsoidal or orthometric heights etc.), the allocation of the known points at a concrete area, the number of neurons and the number of hidden layers are examined. The results are evaluated by means of the achieved RMSEs, they are compared to each other and to the initial approximation by a polynomial interpolation using GNSS/leveling data. For the trial run an urban region of Athens city was used, where 37 points of known geoid undulations are located at 12Km2 area. Useful diagrams illustrate the evaluation of the 176 BPANNs that were tested. It is concluded that the number of the known points is not as crucial as their regular and equidistant allocation. Also the increment of neurons in the hidden layers, optimize the results. Moreover simple input data set with two or three neurons including the coordinates of the known points is adequate as it provides better assessments.

One of the main subjects of Geodesy is the moni-toring of position changes of artificial structures (buildings,dams, bridges etc.). Such position changes can be caused by avariety of reasons such as vehicles for cable bridges and earth-quakes. Various mathematical models have been developed inorder to monitor and to analyze this phenomenon. This studypresents the main models which are used by geodesists for thedescription of points’displacements. These are the descriptivemodels (which are separated into the congruence and the ki-nematic ones) and the cause-response models (which are sep-arated into the static and the dynamic). Moreover, severalmodels, which are based on time series analysis and are usedmainly for the prediction of financial parameters, are referredin parallel. These are the smoothing models, the time seriesdecomposition models, and the ARIMA models. All theabovementioned models are discussed and compared in orderto emerge their advantages, disadvantages, and limitations.The goal of this study is to substantiate which of these modelscould be used with reliability for prediction of displacements.A case study using the most appropriate models is carried out.The experiment deals with the prediction of displacements ofa set of permanent GNSS stations. The results proved that thelinear kinematic models have the best performance, in com-parison with the other examined models.

In recent years, Wireless Sensor Networks (WSNs) have rapidly evolved and now comprise a powerful tool in monitoring and observation of the natural environment, among other fields. The use of WSNs is critical in early warning systems, which are of high importance today. In fact, WSNs are adopted more and more in various applications, e.g. for fire or deformation detection. The optimum deployment of sensors is a multi-dimensional problem, which has two main components; network and positioning approach. Although lots of work has dealt with the issue, most of it emphasizes on mere network approach (communication, energy consumption) and not on the topography (positioning) of the sensors in achieving ideal geometry. In some cases, it is hard or even impossible to achieve perfect geometry in nodes’ deployment. The ideal and desirable scenario of nodes arranged in square or hexagonal grid would raise extremely the cost of the network, especially in unfriendly or hostile environments. In such environments the positions of the sensors have to be chosen among a list of possible points, which in most cases are randomly distributed. This constraint has to be taken under consideration during the WSN planning. Full geographical coverage is in some applications of the same, if not of greater, importance than the network coverage. Cost is a crucial factor at network planning and given that resources are often limited, what matters, is to cover the whole area with the minimum number of sensors. This paper suggests a deployment method for nodes, in large scale and high density WSNs, based on Centroidal Voronoi Tessellation (CVT). It approximates the solution through the geometry of the random points and proposes a deployment plan, for the given characteristics of the study area, in order to achieve a deployment as near as possible to the ideal one.

In recent years, Wireless Sensor Networks (WSNs) have rapidly evolved and now comprise a powerful tool in monitoring and observation of the natural environment, among other fields. The use of WSNs is critical in early warning systems, which are of high importance today. In fact, WSNs are adopted more and more in various applications, e.g. for fire or deformation detection. The optimum deployment of sensors is a multi-dimensional problem, and has two main components; network and positioning approach. Lots of work has dealt with the issue, and one can find several solutions for sensor deployment either achieving ideal network topology or achieving fine geometry. In most cases, it is hard or even impossible to achieve perfect geometry in nodes’ deployment. The desirable scenario of nodes arranged in square or triangular grid would raise extremely the cost of the network, especially in unfriendly or hostile environments. However the user wants to know how much does the deployment plan, approximates the ideal geometry. A geometry as near as possible to the ideal one, minimizes the numbers of sensors needed, which subsequently means less costs for the entire network. This paper suggests an evaluation method for 2D Wireless Sensor Networks, concerning the geometry of the distributed sensors, in large scale WSNs. It approximates the solution comparing the random TIN that the nodes of the network form, with the ideal geometry, i.e. the regular equilateral triangle grid. The user knows a priori, how much does the proposed deployment plan, achieves a deployment as near as possible to the ideal one, for the given characteristics of the study area.

The outstanding Red Beach in Santorini, a famous volcanic island in the Aegean Sea in the territory of Greece, exhibits extended rockfall instabilities along its cliffs, placing its highly frequented touristic zones at high risk. This study aimed to generate an engineering geological interpretation of these instabilities and to evaluate the degree of the rockfall potential in relation to the natural evolution of the beach. A detailed field survey of the engineering geological conditions and thorough scanning of the cliffs using terrestrial scanning (LiDAR) combined with accurate geodetic survey fac¸ade plans, enabled the detection of cinematically unstable sections. A semiautomated qualitative method for evaluating the site-specific landslide potential was also performed here using an unmanned aerial vehicle, which executed several flights around the research area 3.5 years after LiDAR scanning. The resulting products, namely a digital surface model, an orthophotograph and point clouds, were compared with the LiDAR data to evaluate the behavior of the volcanic formations at the cliff and the rockfall potential. The Red Beach cliff, mainly composed of volcanic scoria cones, was found to be very challenging case for determining a feasible engineering geological solution. Its numerous requirements with respect to rockfall control and stabilization in conjunction with the necessity of maintaining the landscape’s natural beauty and preserving the adjacent archeological site further complicated the problem. However, stabilization to prevent rock falls will provoke a disruption of the balance between the sea-induced erosion and the supply of material that originates from rock falls of the natural slopes toward the beach that could put the existence of the Red Beach in significant danger. A feasible engineering geological solution for stabilizing the cliffs was investigated by evaluating all the possible protective and prevent measures. However, whether any of these measures are acceptable is doubtful.

This paper presents a combined field-monitoring and numerical-analysis study. The aim is to examine the influence of reservoir level fluctuations on the settlements of embankment dams by analysing the long-term monitored response of a well-instrumented dam. The field data from three independent monitoring schemes over 25 years are analysed and show a consistent settlement trend with the time. A relevant statistical analysis identifies a strong correlation between the frequency of fluctuations of the settlements and the reservoir level changes which suggests climate-dependent settlements. Finally, hydro-mechanical finite-element analysis of the structural performance of the dam examines the relative effects of soil consolidation and reservoir level changes. It is found that the majority of the dam settlements are due to long-term soil consolidation and that some small fluctuations are due to reservoir level changes.

The study of the astronomical orientation of monuments in Greece has been strengthened over the last decade by the development and application of contemporary methods of measurement and analysis. The study has highlighted important findings related to monuments from the Antiquity up to the modern era. This study includes monuments of the classical antiquity, early Christian basilicas, Byzantine temples and mosques. However, an equally important Monument category is the ancient theatres. These monuments due to both their size and usefulness became the subject of study in this paper. This paper presents the results of a systematic research concerning the determination of the astronomical orientation of six ancient theatres in Greece. At the same time, the interpretation of their orientation and their possible relation to the mythology, the position and movement of constellations and the topography of their site is also studied. The geometric data produced with modern accurate methods of measurement and analysis certainly contributes to a more thorough study and interpretation of the placement and orientation of such large ancient constructions. This systematic research is carried out for six of the most important theatres in Greece. These are the ancient theatres of Dionysus, Delphi, Epidaurus, Ancient Epidaurus, Argos and Sicyon.

Forecasting is one of the most growing areas in most sciences attracting the attention of many researchers for more extensive study. Therefore, the goal of this study is to develop an integrated forecasting methodology based on an Artificial Neural Network (ANN), which is a modern and attractive intelligent technique. The final result is to provide short-term and long-term forecasts for changing the position of points, i.e. the displacement or deformation of the surface they belong to. The motivation was the combination of two thoughts, the introduction of the concept of forecasting in most scientific disciplines (e.g. economics, medicine) and the desire to know the future behavior and location of a construction or an area of the natural earth surface. This methodology was designed to be accurate, stable and general in deferent kind of geodetic data. The basic procedures, which are involved, are the definition of the problem, the data pre-processing, the definition of the most suitable ANN, the evaluation using the proper criteria and the production and use of forecasts. The methodology gives great importance to the stages of the pre-processing and the evaluation. The forecasting intervals are also emphasized. Finally the most appropriate ANN is presented and evaluated also it is proved that the use of ANNs in order to make short-term and long-term forecasts gives more accurate forecasts compared to other conventional-statistical forecasting methods.

It has been confirmed by many researchers in the past, like Dinsmoor, Heinrich Nissen, Norman Lockyer and Orlandos, that the orientation of the ancient Greek monuments it is not accidental. Also the same is true for monuments of other cultures. Previous years this research was carried out by simple instrumentation like compass and simple calculations due to the lack of computers. Today for the same research there is the possibility of using modern instrumentation and more accurate calculations in order to acquire more accurate and reliable results.

This paper presents a thorough research of monuments astronomical orientation based on the modern state-of-the-art geodetic and astrogeodetic measurements and data analysis. The acquisition of these data permit the acquirement of an astronomically oriented digital plan of the monument, a digital diagram of the perceptible horizon around the monument and a digital reconstruction of the apparent path of the Sun, as it rises above the horizon at characteristic dates. The data reduction procedures are reliable and lead to an accurate determination of monument’s astronomical orientation. The study of this orientation relative to the Sun’s circle reveals significant correlations with the days of their celebration and the adjacent monuments. Here the foundings for the ancient Greek temples of Parthenon and Hephaisteion in Athens, Poseidon at Cape Sounion, Zeus and Hera in Olympia are presented.

The Holy Aedicule situated inside the Church of the Resurrection in the Old City of Jerusalem is the holiest Christian site in the world. For ensuring the sustainability of the Holy Aedicule, continuous, as well as periodic, monitoring using advanced equipment is crucial. The structural health monitoring process, as part of an overall management plan, will contribute in real time, through appropriate risk analysis and documentation, so that all relevant Christian Communities can take appropriate measures for the preservation of the structure. This paper describes the monitoring project and the equipment installed at the site during the restoration works. Main risks identified by the diagnostic campaign were tomb microclimatic variations as a result of the enormous number of visitors and Jerusalem climatic data, rising damp, seismic hazard, and structure movements during and after the completion of the restoration works. The installed instrumentation includes air temperature and relative humidity sensors, moisture content sensors for masonry materials, and a geodetic total station and a network of accelerometers for the continuous monitoring of the static and dynamic behavior of the monument, respectively. Thus, the remote monitoring and assessment of various risks to the monument is possible in real time.

A total geodetic methodology is being presented for the simultaneous real-time monitoring of two or more points on a given bridge. The methodology is based on the synchronization of two high accuracy and dexterous total stations. The application was carried out on the Halkida Bridge. The geospatial data is presented in time series. In addition, the determination of the main frequency of oscillation was calculated by using the FFT analysis.

As many studies worldwide [25], [6], [9], [17] have proven, there is a significant reason on the study of a monument. This is the actual orientation that the founders gave to the monument during its foundation. The orientation of a monument, especially a religious one, follows some strict rules according to each religion, tradition and belief. Today, the orientation of a monument may be determined and registered accurately and easily thanks to advanced technology. Especially if astrogeodetic measurement methods are being used then the orientation may be detected with adequate accuracy. This gives future generation’s reliable information which can facilitate for a better understanding on the purpose behind the erecting of each monument. This paper presents the results of two research programs, which focused on this subject. In order to disseminate the results of these two projects worldwide, the information, is organized in database. Two different software were used, Macromedia and ArcGIS. The ease of use and the various options of usage will be discussed as will the final results.

This paper deals with the comparison of the minimum constraints of the least squares methods that are used for the adjustment of a 3D monitoring network. The comparison is applied for the 3D geodetic network that was established in the site of the Holy Aedicule of the Holy Sepulchre in Jerusalem during the rehabilitation works (2016 - 2017). The permanent 3D monitoring geodetic network was implemented with special benchmarks. This network was measured at 8 different times from July 2016 to January 2017, in order to allow the displacements’ control of the network.

Two methods of minimum constraints adjustment are studied, minimum external and inner constraints. The main difference between these methods is the way each of them overcome the datum deficiency. External constraints require a minimum of known point coordinates and line direction, while inner constraints overcome control problem by using a set of constraints equations.

The network of the Aedicule is being adjusted for every phase, using both methods of minimum constraints. Adjusting the Holy Aedicule network with the external constraints, the accuracy of the determination is better than ±1mm for 95% confidence level, while the absolute and relative displacements are calculated using triaxial ellipsoids. Absolute displacements are equal to 4.1mm. Using inner constraints, the accuracy of determination is better than ±0.5mm for the same confidence level and the absolute displacements equals to 3.8mm.

Through error ellipsoids is proven that inner constraints lead to absolute error ellipsoids 60% smaller than using external constraints, while the displacement vectors do not differ notably, concluding that the sensitivity (i.e. possibility to detect displacements) of the network increases. The results are visually presented with diagrams.

Global Navigation Satellite Systems (GNSS) are currently widely used for deformation data collection. Numerous of receivers are installed on structures like bridges and dams, in order to monitor their operation and health conditions. The technological advancement and installation of many networks of permanent and continuously operated reference stations (CORS) have resulted in their extensive use for monitoring purposes. Each one of the GNSS receivers is connected with a reference station, to perform the measurements.

Although the use of GNSS receivers and a proper reference station has been scientifically proved that horizontal and vertical accuracies of about ±10-15mm can be achieved, the distance limitations of using a permanent reference station for deformation monitoring, is a crucial parameter. In this paper, the influence of the distance, between a monitor receiver and the reference station, to the achieved accuracy is investigated. The study involves measurements by single and dual frequency receivers at various conditions. These refer to the methodology being used for the measurements (Single Base and VRS), and the distance between the reference station and GNSS receiver, which fluctuates from 50m to 25km.

Regarding the results, the values of these distances are studied in order to examine the necessity and usefulness of using virtual stations, which are every time created at a different close distance to the monitored facility. Also, the least time between the different sets of measurements, in order for the deformation time series to be created, is concluded. Finally, the relation between the distance and the achieved accuracy is determined, through mathematical modelling.

The vertical displacements of control points, which are inaccessible using the classical method of geometric levelling, can be determined using the method of Trigonometric Levelling, In this article, the errors appeared in determining vertical displacements with this method are discussed. Also, special reference is made to the error caused by the change of the refraction coefficient, Using the proposed solution, the determination of the vertical displacement and the determination of the change of the refraction coefficient can be done simultaneously.

This paper deals with a Geodetic method for fast and accurate Surveying and Mapping of very steep and rocky ground surfaces. A review of the existing methods and instrumentation is given while the investigation concerning the instrumentation is focused on modern Total Stations that may function without reflectors and allow for the fast and accurate positioning of inaccessible points in a local 3d reference frame. Emphasis is given to the optimal presentation of the results (mapping) in order to allow for easy access to other Geoscientists that have to carry out any kind of work on the site. The method was applied for the Surveying and Mapping of a very steep rocky ground surface of the Mythimna fortress on the island of Lesvos, where there is a need for supporting works in order to prevent the fall of rocks.

This work presents a method for the thorough research of the orientation of monuments, based on state-of-the-art geodetic and astronomical measurements. The proposed measurement and data reduction procedures are rigorous and lead to an accurate determination of the orientation of a monument. The term “orientation” collectively refers to: the astronomically oriented plan of the monument, the diagram of the perceptible horizon around the monument and the diagram of the apparent path of the Sun (or other star) as it rises above the horizon at characteristic dates. Then, the orientation is interpreted in terms of other, mostly cultural, information about the scope of the monument and in combination with its time of construction. In retrospect, therefore, the proposed method provides a new, independent way for the confirmation or the determination of the time of construction of the monument within a narrow chronological range.

An analysis of the method is given (including geodetic and astronomic observations and data reduction). The presentation of the method is best illustrated by the parallel discussion of a particular application, at the church of the Great Meteoro Monastery (within the “Meteora Monastic Community” in Central Greece). The performed measurements are described, accompanied by the corresponding geometrical diagrams. The orientation of the church is discussed in connection with the celebration date at the time of construction. Finally, useful conclusions are drawn about the geometrical characteristics of the monument and the meticulous attention shown by its constructors.

Application of the proposed method to other monuments is of great significance, since it will provide the geometric framework for a database of oriented monuments (in the form of a Geographical Information System), which will be very helpful for the study and preservation of our cultural heritage.

Surveying networks are usually computed using either terrestrial observations or GPS observations. Occasionally, however, various reasons (efficiency, lack of particular observations, etc.) give rise to the need for the combination of both kinds of measurements. This paper attempts to examine the reasons leading to such a combination, the basic issues involved and, subsequently, to evaluate the combination-results in terms of accuracy through a network case study. The network has been measured during two summer courses on the Geodesy module on a Greek island by N.T.U.A. It consists of six points that are apart at distances that vary from 500m to 2 km. Three network solutions were carried out for comparison needs. The first solution used only GPS measurements, while the second used only terrestrial ones. The third solution involved with the combination of the GPS measurements and the terrestrial measurements. The analysis of the results of the above-mentioned solutions elevates the possibilities of the proceeding and the issues that need to be taken into consideration in such an attempt.

Calibration is a procedure, which assesses characteristics of components of a measurement system or even the complete operational system. This paper makes a review of the indispensable tests that must be applied at digital theodolites, which need to be calibrated in arrange time period frame for their proper function before or after their use in fieldworks. These tests also certify the industrial prescribed measuring precision of the instrument. The following tests should be applied: for the proper function of the optical or laser centering system, for the collimation of the instrument’s cross – hairs, for the proper leveling of the correctness of the indications and the DIN '18723 procedure that assesses the precision of horizontal and vertical angles. An aspect about the determination of the "fundamental accuracy" of a theodolite as given by the DIN '18723 specification is submitted.

An application was carried out in order to prove the efficacy and the easiness of the above tests. Two networks were established, the first one inside the laboratory as the DIN '18723 procedure defines and the second one outside in the field. Special targets were used in order to mark the networks’ points. These targets were chosen after the application of the appropriate distinction tests. Two digital high accuracy total stations, the Leica TDM 5000 and the Trimble DR+ 5605, passed all the tests successfully. The results and the duration of all the tests as well as the procedure are presented and analyzed below.

The mechanical or precise old theodolites have graduated glass circles. In order to least the errors of a random wrong graduation of the instrument’s circle, one should adopt an observation program of several sets of measurements on both telescope’s face positions, by the method of rounds or by the method of directions or by the method of angles measurement. The starting point of measurement in each set must change according to the formula 200g/n, where n is the number of sets, in order to use the entire circle surface in the measurements. The following questions arise immediately. Is it indispensable nowadays to carry out sets of measurements? Is it necessary when using digital theodolites to change the initial reading point on the digital circle while measuring?

An experiment was carried out in order to lead at a new proposal for fast and accurate measurements of directions by using digital theodolites without the traditional procedure of the sets. A network was established in the laboratory. Special and distinct targets marked the points of the network. All the directions between the main pillar and the network’s points were measured by using the mechanical theodolite WILD T2, on both telescope faces and in four sets by the method of the closing rounds. The same angles were also measured by using the digital theodolites Leica TDM 5000, TCA 1800, TCR303 and Trimble DR+ 5605 with repeatable measurements on each target at the same time without following the sets procedure.

The results, the comparison of the values of the calculated angles and the achieved accuracy lead to useful conclusions.

The wide use of laser scanners in many applications for the documentation of several surfaces raises the need to test them in large area surveys.

The aim of this paper is the detection, restriction and explanation of the differences appeared in the final product that is produced by either a modern specific reflectorless total station, with scanning possibilities, or a laser scanner. These differences are related to the accuracy, reliability and the quality information that these instruments provide when they are used for a surface scanning.

The instruments that were used for the experimental applications are: The total station Trimble 5605 DR+ and the Calidus 3D laser scanner. The experiments were carried out on the following surfaces:

• A façade of a building and
• An almost vertical rocky declivity.

The differences that were defined in the final façade plans refer to the comparison of the geometric elements and the differences that were determined at the position of the contour lines on the declivity plans.

The above-mentioned disagreements in the geometric documentation are analyzed, discussed and justified. The use of both measuring systems and methodologies is criticized with criteria such as the precision, the quickness and the completion in accordance with the scale of the documentation.

The accurate geoid determination remains still a difficult task for the geodesists. For this purpose several methods and satellite, gravimetric or land – measured data may be used. The need for this definition is significant as it is the unique opportunity to transform the easy derived ellipsoidal (geometric) heights via GPS measurements to orthometric heights, which will be used in the surveying applications.

The geometric interpolation method allows an accurate determination of the local geoid model, even at the centimeter precision level, based on known either orthometric and ellipsoidal heights of certain points or geoid undulation differences DN between certain points. The accuracy of the derived local geoid model depends on the number of the availiable points, the quality of the orthometric and ellipsoidal heights or the differences DN used and the smoothness of the geoid surface at the concrete area.

This paper attempts to make an approximation of the geoid surface over a small area of a few km2. Two surfaces, the plane and the ellipsoid, have been tested for the best fitting via the least square method as adequate number of known points was available. Furthermore, independent checks were applied to ensure the quality of the arisen model. The evaluation of the results and the achieved accuracy allows us to come up to some very useful conclusions about the success of the applied geometric interpolation method and indicates the applications where the computed model can be used.

This paper deals with a new geodetic methodology for fast and accurate Surveying, Mapping and Monitoring of inaccessible ground surfaces as cliffs, dams, mine walls and rocky declivities.

The existing geodetic surveying method and its combination by the use of modern reflector less total stations allow the fast and accurate positioning of inaccessible points up to 800m, in a local 3D reference frame.

The methodology is mainly based on the capability of the total station to automatically sweep the surface by means of the scanning mode, which takes automatic measurements at defined interval within a predetermined by the user window. The advantage is that the coordinates x, y, z, of an adequate number of points can be quickly determined.

The result of the methodology is the creation of 3d Digital Terrestrial Model (DTM) of the surface by an accuracy of about ±2cm. The DTM allows the drawing of horizontal and vertical sections at any position. Additionally, the accurate determination of the main characteristics of the surface as planes inclinations, borders of big rocks, peaks and crevices, empty space among the rocks, is feasible. It is also easy to achieve the monitoring of the surface position.

The accurate DTM offers easy access to other geoscientists that have to carry out any kind of work on the site.

The method was applied for:

• the Surveying and Mapping of a high (about 50m) and long (about 400m) rocky ground surface, where there is a need for supporting works in order to prevent the fall of rocks.
• The Monitoring of the deformation of a dangerous cliff, which crumbles on the national road.

This paper proposes a convenient and easy to perform method for the determination of accurate orthometric height differences. The Accurate Trigonometric Heighting (ATH) is based on the trigonometric heighting. The ATH rejects all the disadvantages of trigonometric heighting, such as the measurement of the height of the instrument and the target, and the errors caused by the geodetic refraction and the curvature of the Earth.

A reflectorless total station is indispensable for the measurements, as the method can be applied either between accessible or inaccessible points.

The precision of the method varies between ±0.5mm to ±1.5mm, is analogous to the spirit leveling and depends mainly on the accuracy of the zenith angles measurement.

The ATH is described in detail and also, an application is presented in order to elevate its effectiveness and to certify its accuracy.

The world’s first total station to incorporate the very latest digital imaging technology to enhance Total Station fieldwork and extend the range of applications for the total station has been presented by Topcon just a few years ago. The implementation of imaging technology allows the image seen through the telescope to be viewed on the display screen of the instrument. This not only makes it easy to point the telescope to the required object for measurement, but instead of only the traditional map view of the surveyed points on the screen, you now see the measured points and lines appear on the real view of the area being measured. In addition you can now “Capture Reality” by storing the digital image along with the measurement data. In this paper the idea of photogrammetrically exploiting the images taken by this total station in conjunction to the recorded angles is thoroughly examined, as far as monoscopic images and plane objects is concerned for a start. An algorithm has been developed to produce rectified images without the need for any control points on the object. The implementation range and its limitations are examined and the results assessed for their accuracy

In recent years imaging total stations appeared, offering the possibility if measuring angles and distances through pointing enabled via a digital screen. These innovative ways of pointing as well as the incorporation of a digital camera in the total station need calibration and thorough control.

In this paper a methodology both far calibrating the digital (CCD) camera οf the imaging total stations as well as for determining the elements οf their interior orientation is developed and presented. The main aim is the determination οf the calibrated focal length οf the CCD camera, the position οf the principal point (xο, yο), the characteristic curve οf the radial distortion (#r) and the affinity, i.e. the geometric distortion οf the pixel.

The proposed methodology serves to investigate the possibility and the reliability οf determining the parameters οf the interior orientation οf the digital camera using suitable algorithms, as well as their repeatability. The results are compared with the nominal values given by the manufacturer. Finally, several experimental tests are presented for various taking distances between the total station and the object, in order to establish possible variations οf the parameter values and help towards their modeling.

This paper presents a detailed description of the methodologies and the actions taken for determining and monitoring the deformations and micro-movements of the post-byzantine Church of Megali Panayia in Samarina. An assessment is also provided of the first results obtained from the repeated observations and their combined adjustment, followed by a discussion on their reliability. The reported analysis focuses on the following crucial aspects: the accuracy and the stability of georeferencing, which is fundamental to make comparisons between different multi-temporal measurements; and the computation of deformation based on the survey observations between the established control points. Emphasis is given to the presentation of the results using a detailed 3D model of the church, created from terrestrial laser scanner point clouds. The methodology applied involves the analytical combination of multi-source measurements, i.e. GPS observations and classical surveying observations using appropriate high-end theodolites and total stations, in order to achieve the highest possible accuracy. The use of a time-of-flight laser scanner provided data for the 3D model creation. From the re-measuring of this network four times during a five month period and by comparing and analyzing the results of all measurements, it was possible to detect and obtain crucial information about the building’s structural behaviour and the surrounding terrain’s displacements and deformations. The results show a tendency of the surrounding ground to slide towards the northeast direction in a very slow tempo. However the observed displacements between characteristic control points on the building itself tend to demonstrate a slow varying periodic effect. The internal accuracy achieved in absolute positioning of the network points is of the order of ±2-3 millimeters.

The development of high end total stations in recent years has been quite rapid, particularly in regard to the range and the uncertainty in measuring distances. In the fourth part of the ISO 17123-4, the process of the metrological check and the calculation of the measurement uncertainty of any distance, provided by total stations, are included.

In this paper, we will investigate how functional and flexible an outdoor control baseline is for determining the measurement of uncertainty in distances, in accordance with ISO. The idea for the establishment of a convenient outdoor control baseline focuses on the alternative realization of its pillars, by using special manufactured detachable stands. This minimizes the cost and the construction time.

An experiment is carried out at a designated site, using two modern total stations of high precision. The methodology and all the necessary equipment (devices - components) are referred to and described. The analysis of the measurements is followed by using the least squares method and the results are presented. The results are then compared with those determined for both the total stations, during their recent metrological check abroad, at the manufacture’s original outdoor baseline.

The prototype, manufactured detachable stand, which is being proposed to be utilized for the realization of such an outdoor control baseline, is presented. The advantages, which make this baseline more convenient, flexible and more cost-effective than those which already exist abroad, are noted on. Consequently, obvious are the financial benefits of the use of such a control baseline, as well as the ease in its placement combined with the simplicity in the site selection.

Water depth estimation based on echo-sounding principles is the most widespread technique used in bathymetric / hydrographic surveying worldwide. The working principle of the method resides on the accurate / reliable measurement of the time interval that necessitates between the transmission of an echo-sound pulse and its reflected reception by the sensor; a procedure that heavily depends on the assessment of the transmission of echo-sound velocity in water.

In this process, in order to ensure successful depth estimation deems necessary to apply various corrections and reductions in the raw measurements due to a number of error sources found in the assessment of echo-sound velocity (ought to variations in water temperature, pressure and salinity), and errors relating to the operational (electromechanical) aspect of the echo-sounder units.

In this study, a detailed review of the specifications and operating procedures dealing with the calibration of single beam echo-sounders is attempted. Also, the “bar check” calibration method is applied for the calibration of a single beam echo-sounder in the graving docks of Hellenic Shipyards S.A. using a special designed apparatus. The field work undertaken is presented and the results obtained from a number of tests are discussed and evaluated

Artificial Neural Networks (ANNs) are part of the wider category of Computational Intelligence, which today constitutes one of the most important and most rapid developing fields not only in the computer science in general but also in the Artificial Intelligence. Even if initially their use started only in the sector of neuroscience, now the ANNs are widely used in various scientific regions such as medicine, economy, defence, meteorology, manufactures, biology etc. Moreover ANNs except from their import in many different scientific regions, they also have many different applications such as classification, regrouping, approach of interrelations etc.

This study presents the main aspects of the ANNs' structure and their modus operenti. Α systematic research of their use in various fields of Metrology, both in the fields of natural and chemical measurements and analyses, is performed.

After this research it was found that ANNs have already been used in nanometrology, and more specifically in the improvement of some special laser appliances which measures small objects' dimensions. Moreover, they have been already used in the determination - forecast of corrections in the values of the world coordinated time UTC. The use of ANNs is also met in the scientific region of clinical Metrology, for the improvement of diagnostics of process, while they are systematically incorporated as softwares in special biosensors, which are used in the detection of remains of pesticides improving the results of measurements. Finally, scientific areas of the Metrology, in which the technique of ANN could be used alternatively or complementary with other methods, are presented.

GNSS measurements are widely used for the monitoring of several structures’ deformations such as dams, bridges, high-rise buildings as well as landslides and earth crustal movements. In most cases the use of GNSS receivers is more convenient as it ensures continuous measurements and provides unmanned observations, long or short baselines measurement without visibility between the points. Moreover the accuracy of the static relative positioning reaches the sub-cm level.

According to the usual procedure both horizontal and vertical change vectors of each point’s position are calculated in order to examine whether they should be considered as displacements or they are within the noise of the measurements.

As many commercial GNSS software packages don’t provide the full variance – covariance (VCV) matrix as an output, there is often a miscalculation of the absolute and relative error ellipses or ellipsoids for any confidence level. Moreover the baselines’ solution usually provides unrealistically optimistic standard errors. Thus it is often ignored or empirically scaled. The right weight estimation is needed in order to produce an objective VCV matrix from the network adjustment.

This work presents a complete, reliable processing methodology for 3d monitoring by using GNSS measurements. This processing methodology allows the use of the initial baselines measurements and leads to analytical results according to the least squares method and the law of propagation of errors.

Also the paper uses a specific technique for the preferred definition of the weights in order to be used for the unequal weight adjustment.

The network adjustment is carried out in the geocentric reference system by using linear equations and the indirect observations method. The full objective VCV matrix of the network is provided. The appropriate full rotation matrices are used in order to transform the displacement vectors as well as their variances and covariances in a local oriented plane projection in order to be more perceptible and useful.

Finally, the limitations of the proposed procedure are represented by the calculation of the difference to the error ellipses when the full VCV matrix is used.

The aim of this work is the evaluation of a monitoring network depending on the measurement method and the data processing methodology.

The sensitivity of a monitoring network is a crucial parameter as it influences the magnitude of the displacement which can be detected for a concrete confidence level. The construction and placement of the network points is very important in order to facilitate forced centering and efficient surveying instrument setup. Also ensures the ease and the quickness of the measurements.

This research is carried out by using a prototype monitoring network, which was established on 2012 at the plant of Electricity Authority of Cyprus in Vassilikos.

At first the construction of the network’s pillars is described in detail. Also the design and establishment time required is referred. Additionally the cost of the network is criticized as well as the difficulties of the process and possible missteps are presented.

The network was measured both by using GNSS receivers and first order total station. Four separate adjustments of the network were carried out. These adjustments include the GNSS measurements and the terrestrial measurements in 1D, 2D and 3D. The results, namely the points’ coordinates and their uncertainties are compared to each other in order to bring forth the best procedure, which provides simultaneously the minimum errors and which requires the minimum effort.

The goal is the improvement of the procedure as well as the detection of the elements which increase the uncertainty of the network’s results.

n this paper the establishment of a standard external calibration field for total stations is presented. This field is founded by a research program of the School of Rural & Surveying Engineering of NTUA and Geotech ltd Company in accordance to the requirements of the corresponding ISO, at the site of the Olympic Rowing at Schinias, in Attica. A flexible baseline is created for the distance check, according to the instructions, which are described in ISO 17123-4.

The implementation originality of this baseline is that it is marked by special portable metallic pillars instead of cement pillars, creating an alignment of 2Km. The way of the installation of this baseline proved to be low cost, more functional and convenient than other baselines in Europe or world wide. It was also proved that the baseline meets the accuracy requirements of the calibration process.

Additionally at the same site two more check and calibration fields are created for directions (horizontal & vertical) according to the ISO 17123-3 instructions.

Special distinctive targets are used for the points’ marking that provides permanence - durability and flexibility to their installation and their use.

Moreover the baseline can be used for the check of GNSS receivers for the RTK procedure according to the ISO 17123-8.

Finally the first indicative results of the check of two total stations are presented.

The development of geodetic measuring instruments the last 25 years is rapid. From the simple instruments for distance measurements (tapes), angle measurements (mechanical theodolites), and height differences measurements (levels), run into the abrupt devolvement of digital systems that can measure distances, angles and height differences, by digital way (total stations, digital levels). Also important and decisive is the evolution of satellite systems (GNSS).

However, which is the corresponding support in Greece? What happens today in the sector of checking and calibration of the geodetic instruments and their equipments? What is defined by the legislation for the use of these instruments in the infrastructure works?

This work presents some accredited calibration laboratories worldwide and also some attempts that were made in Greece to this direction. The efforts, the lacks and also the problems that occur in order to create accredited calibration laboratories in Greece are registered.

Obviously the goal is to record and recognize the real situation but mainly is to emerge the significant role of the accredited laboratories for the calibration of geodetic instrumentation today, that the use of such multi systems for the measurement is wide spread to many users. Also the accuracy requirements for the technical constructions are very high.

Final aim is the sensitization of the public sector (as Universities) as well as private concerns (as representative companies), in order to create these conditions which will allow the action and service of reliable accredited laboratories in Greece.

The present work presents an engineering geological assessment using terrestrial laser scanning for the study of stabilization of a rock slope in Santorini island that has suffered from several rock slide incidents. The use of LiDar laser scanning and focused surveying provided valuable data for the engineering geological zonation of the area and the rock block quantification for the stability analysis.In order to prevent failure and the accompanied consequences, slope stability analysis and various mitigation methods were examined based on the site’s geological and geotechnical conditions, cost, local architecture restrictions and constructability.

The National Technical University of Athens undertook the compilation of an "Integrated Diagnostic Research Project and Strategic Planning for Materials, Interventions Conservation and Rehabilitation of the Holy Aedicule of the Church of the Holy Sepulchrein Jerusalem". This paper focuseson the work merging the geometric documentation with the characterization of materials, the identification of building phases and the diagnosis of decay and pathology through the use of analytical and non-destructive techniques. Through this integrated approach, i.e. through the documentation and characterization of the building materials, through the diagnosis of decay and pathology, through the accurate geometric documentation of the building and through the non-destructive prospection of its internal structure, it was feasible to identify the construction phases of the Holy Aedicule, identifying the remnants of the preserved earlier constructions and the original monolithic Tomb. This work, thus, demonstratesthat the adoptionofan interdisciplinary approach for integrated documentation is a powerful tool for a better understanding of monuments, both in terms of its structural integrity, as well as in terms of its state of preservation, both prerequisites for effective rehabilitation

This paper presents a finite-element analysis of the long-term (>25 years) deformation behav-iourof a well-instrumented earth dam. The aim is to examine the influence of (a) consolidation, (b) reservoir level changes and (c) seismic activity on the global deformations of embankment dams. Kouris earth dam, which is the largest dam in Cyprus, is considered as a well-documented case study and its monitored long-term deformation behaviour is analysed. Firstly, the field displacement data over 25 years from three inde-pendent monitoring schemes are processed and analysed and show a consistent settlement trend with the time. Subsequently, two-dimensional plane-strain coupled hydro-mechanical nonlinear finite-element analyses of the dam are conducted which consider plasticity, small-strain stiffness and permeability of the dam materials. The entire stress history of the dam is modelled, including staged construction, reservoir impoundment, con-solidation and seasonal reservoir level changes. From both the finite-element analysis and the field data pro-cessing, it is shown that (a) seasonal reservoir level changesresult in small fluctuations of dam settlements (i.e. vertical displacements), (b) horizontal dam crest displacements are insensitive to reservoir level changes and (c) the majority of the total settlements is due to soil consolidation.

Earth dams are massive water-retaining structures that are used widely in the world for irrigation, water supply and hydroelectric energy generation. Many such dams are built every year and the International Committee on Large Dams (ICOLD) has gathered together experts from the world to work on preparing guidelines for design, construction and monitoring of such massive infrastructure. A potential failure of a large dam may potentially have significant effects on a huge area downstream, as the sudden release of the large volume of retained water can travel for large distances and destroy entire cities and even result in unfortunate fatalities.

It is therefore important to recognise the potential causes of failure of such dams and provide timely and effective measures to prevent any degradation or loss of stability. The main threats for dams are seismic activity, internal erosion, faulting and seasonal climate variations. The latter factor, i.e. climate changes, has not been studied widely and therefore there is a need for further understanding of the problem. In arid and tropical climates, e.g. the Mediterranean, Middle East, south Asia, large changes in the temperature and rainfall cause significant variations in the upstream reservoir level. This results in the dam rockfill undergoing cycles of wetting and drying which further causes permanent displacements and potentially cracking. Such structural response needs to be closely monitored, so that any potential leakage (and therefore erosion) is prevented.

This keynote paper presents an experimental study to investigate the effects of seasonal climate variations on the deformations of earth dams. A well-instrumented dam in Cyprus, the Kouris earth dam, which is the largest dam in the country is used as a case study. Long-term monitoring data from three-independent and different instrumentation sets are collected, processed and analysed. A periodic variation in the crest settlements is identified and thus relevant statistical analysis is performed to identify the dominant frequencies of fluctuations and to examine any relation between the dam crest settlements and the reservoir level changes. Subsequently, a nonlinear coupled hydro-mechanical finite element analysis is performed which models the entire stress history of the dam, i.e. layered construction, reservoir impoundment, consolidation and reservoir level changes. The latter finite element analysis attempts to identify the relative effects of soil consolidation and reservoir level changes on the induced dam displacements.

Until now, an ISO standard has not been set out to define a methodology for the Total stations (TS) calibration for directions. This process is necessary in order to safely use such instruments in infrastructure and survey works.

In this paper, an integrated methodology for calibration of total stations is presented and developed, using as background measurements obtained from the checking methodology of Total stations in accordance with ISO 17123-3.

The mathematical models for the two calibration procedures are presented, which are related to the calculation of the residuals of instrument’s measurement and the determination of the uncertainty equation.

The multicriteria evaluation technique is applied in order to select and propose the most appropriate procedure.

Then the calibration methodology for the external fields, which were installed at the Olympic Rowing at Schinias in the prefecture of Attica, is carried out in order to be feasible the TSs calibration.

Finally, the calibration of four TSs is carried out. The results are presented in the form of tables and diagrams and demonstrate the usability and effectiveness of the proposed calibration methodology for directions in external control fields.

The Application of the calibration methodology of a TS requires one and a half hours of measurements to confirm or not the uncertainty, accuracy and reliability of direction measurement while calculating any systematic or random error that is included in the measurements of the TS under calibration

In this work initially a historical retrospection and recording of the evolution of geodetic measuring systems is carried out at a global level. This retrospection starts from dioptra and ends to the modern measuring systems that perform automatic aiming or they have no telescope as operate via a touch screen.

This historical retrospection starts from the time of Heron of Alexandria, in 120 BC, who invented the first instrument for measuring angles, after to the time of the manufacture and operation of mechanical theodolites (1730) and later to the period of the optomechanical theodolites (1926), and the electromagnetic distance measuring instruments (1957). Finally we arrive nowadays at the time of measuring angles and distances by using modern measuring systems that measure distances with reflector or reflectorless with accuracy up to few mμ and angles with high precision while aiming through a digital camera and communicate via a touch screen.

The particularities of the use of the modern geodetic measuring systems are highlighted and also the advantages that offered their continuous improvement over time to the accuracy of the implementation of the survey Engineers fieldworks are mentioned. Also the modern applications where these systems are used and their requirements for precision and reliability, which now reach the few μm are referred.

A total deficit of institutionalized modern check and calibration procedures is noted. The check procedures could not simultaneously follow the rapid evolution of geodetic measurement systems, so it is immediately necessary to adapt and to modify the control procedures and to upgrade them to control-calibration procedures.

The aim is to highlight the need to modernize the procedures for the control of the modern geodetic measuring systems and the lack of modern and reliable procedures for their calibration in order to directly study and define new ones that will guarantee the accuracy, the reliability and the quality of the provided by the survey engineers works and products.

Holy Aedicule inside the Holy Selphuchre Temple is an emblematic monument of the Christianity. The installation of a monitoring system during the rehabilitation works, aimed to the record and evaluation of the critical risks affecting the structural integrity of the monument. Regarding the microclimatic conditions, a wireless sensor network was installed, for recording air tempera-ture and relative humidity hourly values, inside and around the temple of Holy Aedicule. Main aim is to evaluate the effect of the environment, but also the in-fluence of the thousands of visitors every day. Moreover, since rising damp was found to be one of the main critical risks for the structural integrity of the monument, a wired sensor system was set. With the aid of this system is re-corded materials moisture inside the masonry, at selected areas of different height and orientation. Furthermore, a geodetic total station for monitoring of monuments body positioning and a network of accelerometers for the continu-ous monitoring of the dynamic behavior of the monument were installed. All the above instrumentation achieves, the remote monitoring and assessment of various risks of the monument in real time.

In the past few years, the rapid evolution of the Wireless Sensor Networks (WSNs) made them a powerful tool for monitoring and observing the natural environment. The use of WSNs is critical in early warning systems, which are of high importance today. In fact, WSNs are adopted more and more in various applications, e.g. for fire detection, geohazards monitoring or deformation detection in large scale areas. The spatial distribution of the sensors of a WSN must follow specific criteria. The equilateral triangle grid leads to the maximum coverage with the minimum number of sensors. Nevertheless, in most large-scale outdoor applications, achieving the ideal deployment geometry is hard or even impossible. In such environments the positions of the sensors have to be chosen among a list of possible points, which in most cases are randomly distributed. In order to achieve a geometry as near as possible to the theoretical optimum, the OptEval algorithm has been proposed. It makes use of the Centroidal Voronoi Tessellation (CVT). Although the case studies had the desired results, their simulation took place in the continuous 2D space. There are cases, in which we may not be interested in covering the whole area with sensors, but only a buffer zone surrounding it. In other cases, it may be impossible to cover the area under study due to natural constraints (e.g. lakes, holes etc.). This paper evaluates the effectiveness of the proposed method in an area with holes. Alternative scenarios are examined, by changing the values of the parameters that affect the final result, i.e. the number of the points to be observed, the number of the available sensors and the radius of the sensors.

The need of high accuracy geodetic measurements, especially in the vertical displacements control network, is nowadays extended and thus the thorough investigation of all possible error sources is necessary. Despite the fact of technological improvement the accuracy of geodetic measurements is still limited mainly due to the unpredictable propagation of a sighting line. These error sources are concentrated on the variations of the refractive index; witch either bends or retards the electromagnetic wave path and is caused by air density inhomogeneity, which is in terms influenced by the fluctuations of atmospheric parameters.

The present paper aims to the determination of the dependence between digital height readings and the air temperature as well as the atmospheric pressure by performing repeatable short term measurements. Thus, a stand-alone set up of a high accuracy digital level was developed and both indoor and outdoor experiments were carried out for a time period of several days with a time interval of five minutes. At the same time there were air temperature sensors nodes used, which were mounted on the staff, and a meteorological station.

Hence the additional time series were generated and correlation coefficients were computed in order to investigate as much as the linear relationships as well as the monotonic relationships among the measured parameters. Also the repeatability of the digital level’s height readings was calculated. The basic term is that the meteorological conditions are stable, which means that heat flux effects are not applied (ventilation or convection). Thus moderate and poor correlations were computed between the acquired data.

Earth dams are massive structures retaining large volumes of reservoir-water. They constitute an important part of modern civil infrastructure contributing to water supply, irrigation and power generation. Their structural stability/safety is crucial, as a possible failure of a large dam will lead to a sudden release of huge amounts of water which may potentially lead to damage and casualties in the downstream. It is therefore important to monitor their deformations and the structural health to avoid any such unfortunate events.

This paper presents a comprehensive study on the long-term monitoring of earth dams. A well-documented case, the Kouris dam, which is the largest dam in Cyprus, is examined in detail. The paper consists of three main parts. The first part presents the different types of instrumentation installed and how data processing of the monitoring data is performed. The second part presents the analysis and interpretation of the monitoring data, both in the time- and frequency-domain. The third part presents relevant complementary finite-element analyses of the dam and its calculated long-term response subject to embankment construction, reservoir impoundment, operation and reservoir level fluctuations.

The collected monitoring data exhibit a consistent pattern of long-term crest settlements and downstream deformations. The magnitude of these is compared well to previous monitored dam cases and was therefore expected. It is also shown that frequency analysis reveals a strong correlation between crest settlements and reservoir level fluctuations, suggesting a seasonal variation of dam deformations. Additionally, the finite-element analysis shows that soil consolidation is the dominant mechanism of dam settlements in the short-term, whereas reservoir level fluctuations dominate in the long-term. Finally, the main message of this investigation is that robust and reliable measurements are important and high-quality and accurate monitoring data are substantial for evaluating the long-term structural health monitoring of large earth dams.

The Holy Aedicule of the Holy Sepulchre, an emblematic monument that has survived throughout the centuries, recently underwent a major and demanding rehabilitation under the responsibility of the National Technical University of Athens Interdisciplinary Team. The requirement for reinstating structural integrity to the Holy Aedicule, for preservation of the values it represents and for achieving a sustainable rehabilitation in a demanding environment, demanded a multidisciplinary approach utilizing multispectral monitoring techniques of the successive phases of the Holy Aedicule, prior, during and after the completion of the rehabilitation interventions. Specifically, a thorough geometric documentation was realized involving laser scanning and photogrammetric techniques, in order to obtain a 3D textured model of the Holy Aedicule, prior to the initiation of the works. At this phase, in parallel a diagnostic study was implemented, regarding the building materials and their decay phenomena, utilizing non-destructive techniques that document the surface of the monument and its state of preservation, while providing prospection of its internal structural layers. This information was crucial for the design of the restoration materials and rehabilitation interventions. The next phase involved dismantling of the exterior stone slabs from the facades. The revealed masonry was geometrically documented, to record the morphology of this internal layer and to optimize the design of the required interventions. The geometrical products verified the non-destructive prospection of the Aedicule. During the strengthening interventions the Tomb of Christ was opened, along with an “observation window” within the Tomb Chamber; their interiors were digitally documented, including materials information. Upon completion of the strengthening interventions (grouting, titanium elements, etc.), the columns were reset and the stone facades were reinstalled, and the Aedicule was “freed” from the British metal frame installed seventy years earlier. The final phase involved an interdisciplinary documentation of the rehabilitated structure.