Publications

She has published 86 scientific works

Determination of the "Piece and Friendship" stadium deformations. A vertical control network establishment in the surround area.
Diploma Thesis, 1990
Development of a methodology for astrogeodetic determinations using digital geodetic instruments.
Phd Thesis, 2003

Fast and accurate determination of astronomical coordinates Φ, Λ and azimuth, using a total station and GPS receiver

D. D. Balodimos, R. Korakitis, Ε. Lambrou and G. Pantazis

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.

Accurate determination of the geoidal undulation N

Εvangelia Lambrou, George Pantazis, Dennis D. Balodimos

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.

A standard network to control GPS receivers

Εvangelia Lambrou, George Pantazis

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.

Astrogeodetic study of the orientation of Ancient and Byzantine Monuments: Methodology and first results

Pantazis George, Sinachopoulos Dimitris, Lambrou Evangelia, Korakitis Romylos

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).

On the date of early Christian Basilicas (Central Greece)

George Pantazis and Evangelia Lambrou

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.

Astronomical azimuth determination by the hour angle of Polaris using ordinary total stations

Ε. Lambrou and G. Pantazis

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.

The orientation of Delos’ monuments

George Pantazis, Evangelia Lambrou, Konstantinos Nikolitsas, Maria Papathanassiou, Athanasios Iliodromitis

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.

Investigating the orientation of eleven mosques in Greece

George Pantazis and Evangelia Lambrou

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.

Evaluation of the Credibility of Reflectorless distance measurement

E. Lambrou and G. Pantazis

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.

Special marking of 3d networks’ points for the monitoring of modern constructions

Evangelia Lambrou, George Pantazis and Konstantinos Nikolitsas

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.

Accurate Geoid height differences computation from GNSS data and modern astrogeodetic observations

Εvangelia Lambrou

This work presents the revival of the astrogeodetic observation procedure by means of modern instrumentation and processing. The determination of astronomical coordinates Φ, Λ and the components ξ and η of the deflection of the vertical is achieved with an accuracy that reaches ±0".01

The used method brings to the fore the classical geodetic astronomy actually aided by modern technology. The system of NTUA is used (Lambrou 2003).This system consists of a first order total station connected with a GNSS receiver in order to register time with 1msec.

The same method is applied by changing the instrumentation. An advanced "imaging" total station is used, providing a direct connection to the internet, to a world time server, in order to obtain the necessary accurate time information. This total station runs windows CE and moreover it allows carrying out the observations on a digital screen, as the telescope is not deemed essential anymore. The sightings may be also carried out remotely via a PC’s screen situated anywhere and connected to the internet.

Alternatively, in order to bypass the need of accurate time information, the Laplace equation can be used. Thus the determination of η is achieved. As a limitation, this procedure requires visibility between the points.

By using the corresponding geodetic coordinates φ, λ and azimuth, which are all provided by the GNSS measurements, the deflection of the vertical components (ξ and η) are computed. Thereinafter the geoid undulation differences ΔN are calculated, with few mm accuracy.

By following this procedure, the results are independent from the definition of the local height datum. For this reason, it can improve the global geoid models as it enriches their data in areas characterized by large geoid variations due to rough topography. Finally, this procedure could be used for the unification or the definition of a unified height datum, for a country.

Analysis of the errors of the antenna’s set up at the GNSS measurements

Evangelia Lambrou

Today, the GNSS system (Global Navigation Satellite System) is used for more complicate and accurate applications such as monitoring or stake out works. The truth lies in the fact that in the most of the times not enough attention is paid to the antenna’s setup. Usually, gross errors are found in the antenna’s centering, leveling and in the measurement of its height, which are significant. In this paper, a thoroughly analysis of the above mentioned errors is carried out. The influence of these errors in the calculation of the X, Y, Z Cartesian geocentric coordinates and the φ, λ, h ellipsoid geodetic coordinates of a point P on the earth’s surface, is analyzed and is presented in several diagrams. Also a new convenient method for the accurate measurement of the antenna’s height is presented and it is strongly proposed. The conclusions outline the magnitude of these errors and prove the significance of the antenna’s proper setup at the accurate GNSS applications.

Remote Survey. An Alternative Method for Capturing Data

Evangelia Lambrou

Abstract: As technology in the manufacturing of total stations evolves at rapid speeds, a new era arises for the Surveyor's field work. This paper presents the appropriate instrumentation, the software and the possibilities of communication, which are needed for the Remote survey realization. By engaging in it, the surveyor can sight, measure, help or check his or her collaborators at the field, without having to be at the designated site. Applying the remote survey in specific applications, the user can target, choose and check the targets and also have a complete view of the field work in progress, at any given time from his or her office, his or her home or where ever he or she might be. Ganging up free software and appropriate instrumentation combining with wired or wireless connections, the remote overall control and handling of a total station is achieved without any additional costs. The pros and cons of this procedure are presented. Additionally the first successful results of the remote targeting accuracy, achieved via a computer, according to the ISO17123-3 procedure, are presented. Finally useful discussion and further investigational tips are underlined. The described method is intended for supporting specific surveying applications or scientific and academic researches and not for professional land surveying works.

3D Digital Terrestrial Model Creation Using Image Assisted Total Station and Rapid Prototyping Technology

G. Pantazis, E. Lambrou, S. Polydoras and V. Gotsis

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.

Estimation of the gauging and the calibration time interval for the modern total stations

Evangelia Lambrou and Antonios Antonakakis

The modern TSs (total stations) have reached a very high level in the provided reading and reliability (accuracy and precision) of their measurements. The evolution of the digital technology has helped in this direction. Thus, the TSs can support all requirements for the stake out and monitoring of modern survey engineering and constructions projects. Their complicated manufacturing process and the sensitivity of their components require gauging, adjusting and calibration at certain time intervals. This appears to be the only way in order to assure the precision of measurements provided by the manufacturer and the reliability of the works they are used for. The goal of this paper is to propose a method for the estimation of the gauging time interval for modern TSs, which could be used by any user. More specifically, the indispensable need for the TSs gauging is elevated and documented. All the parameters that influence their operation are registered. A model expressed by a scale of grades is defined, leading thus to an equation for the calculation of the time interval for the next needed gauging and calibration.

Testing and performance evaluation of terrestrial panoramic imaging system in close range documentations

Anastasios – Grammatas Kampouris, Evangelia Lambrou

A new surveying methodology is accomplished by using terrestrial integrated panoramic imaging systems from fixed station. This technique promises to reduce the surveyor’s field work time in some minutes in order to facilitate the visual and geometrical documentation of various objects and enrich the deliverables of the survey. This paper investigates the convenience of the methodology pushing forward the advantages and the disadvantages. Additionally, compares the results of two selected applications which were respectively implemented by conventional terrestrial survey. The experimental applications that were carried out involved in surveying and documenting a building façade and a vertical cylindrical fuel storage tank. The comparison deals with the accuracy achieved and the time needed for the field work as well as for the data processing. The instrumentation used was the Trimble V10 imaging rover and first order total stations. Thus panoramic imagery from fixed stations is proved to be applicable for the most common survey applications as well as building facades and geometric documentation of structures. The provided accuracy of the calculated coordinates is of the order of few centimeters.

Assessment of the Greek Vertical Datum – A case study in central Greece

V.N. Grigoriadis, E. Lambrou, G.S. Vergos, and I.N. Tziavos

In this study, the consistency of the Greek Vertical Datum (GVD) is examined, focusing on an area in central Greece and following similar efforts made in previous researches for the establishment of an International Height Reference System (IHRS). High precision GNSS measurements are available at trigonometric benchmarks located along the Gulf of Corinth, with benchmarks residing on both coasts along. First, the zero-level geopotential value (WoLVD) for the two areas, north and south coast, is determined, based on the classical Helmert theory using GNSS/leveling data and surface geopotential values derived from GOCE-based global geopotential models (GO-DIR-R5, GO-TIM-R5, GOCO05s and GECO) and EGM08. Then, the relative offset between the two areas is estimated while subsets of the computed benchmark values are also examined. Significant inconsistencies are detected that depend on the choice of benchmarks used in the computations.Moreover, a per benchmark analysis showed that the inconsistencies present a random spatial distribution and are attributed mainly to the orthometric height values of the benchmarks. Furthermore, the local WoLVD estimates are compared with previous results related to the GVD and the VD of the Greek islands and the corresponding value adopted by the IHRS. Finally, some remarks are drawn on the feasibility of the unification of the GVD with a global one.

Beyond the boundaries of feasible engineering geological solutions: stability considerations of the spectacular Red Beach cliffs on Santorini Island, Greece

V. Marinos, G. Prountzopoulos, P. Asteriou, G. Papathanassiou, T. Kaklis, G. Pantazis, E. Lambrou, N. Grendas, E. Karantanellis, S. Pavlides

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.

Detecting the Centring Error of Geodetic Instruments over a ground mark through a tribrach based optical plummet

Εvangelia Lambrou & Konstantinos Nikolitsas

Accurate centring is the primal procedure for the setting and the proper operation of geodetic instruments in order to obtain correct measurements.

Different centring means are used through the time from the plumb bob to the laser plummet. The more distributed centring mean, which is examined in this research, is the tribrach with optical plummet; as today, it is used for the setting of a variety of instrumentation as total stations, Global Navigation Satellite System receivers, laser scanners, targets, etc.

This paper develops a procedure for the detection and the assessment of the centring accuracy, which occurs over a ground mark trough a tribrach-based optical plummet. The process is based on the rectification of a single image, which is taken through the tribrach eyepiece. About 150 experimental processes were carried out by using different implementation materials for the ground points, as well as by using different targeting options through the tribrach. The resulting centring errors are presented by several diagrams for all the tested combinations in order to define the length and the direction of the centring error vector. The centring error does not exceed 1 mm by all the combinations, while the mean value is about 0.3 mm. Moreover, the direction of the error vectors presents a systematic orientation which probably expresses the observer’s personal equation and skills. The proposed procedure is assessed as reliable and adequate. Further investigation is proposed in order to examine more types of ground targets and the personal influence of the observer.

The Influence of Deployment Parameters on 2D Wireless Sensor Network by Using a Centroidal Voronoi Tessellation Based Algorithm

Athanasios Iliodromitis, Evangelia Lambrou

The optimum spread of a Wireless Sensor Networks (WSNs) is the main requirement for all the modern applications that use WSNs for the monitoring and the observation of natural environment. The early warning systems e.g. for fire or deformation detection are the main fields that uses this technology as well as the monitoring of other environmental parameters as temperature, humidity, pollution and radiation.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. The OptEval algorithm, using the Centroidal Voronoi Tessellation (CVT), achieves geometry as near as possible to the ideal one, minimizing the numbers of sensors needed, which subsequently means less cost for the entire network. A range - independent index that takes into account the geometry of the distributed sensors is used for the evaluation of the solution, comparing the random TIN, which the nodes of the network form, with the ideal geometry. This paper investigates the features of the above procedure in relation to the main parameters namely the density of points for supervision, the range of the sensor and the number of used sensors .This will provide an useful tool for the immediate assessment of the probable optimum solution, it can create directives for the operation and the efficiency of the deployment as well as for its cost. So, ninety different scenarios are formed for the same area with randomly distributed observation points, changing 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 results follow a pattern which can be taken into consideration for future work. Also has emerged that the most crucial parameter is the range of the sensor which is used. Thus, the users of this method can assess the expected values of coverage percentage and the geometry of the final solution in order to deside for the implementation of the optimum deployment.

Modeling the deviations of the Reflectorless Distance measurement due to the beam’s incident angle

E. Lambrou

As the reflectorless (RL) distance measurements provide exceptional possibilities to the modern surveying projects, the reliability of the measured distances has major significance. However the reflectorless distance measurement is influenced by numerous parameters via a complex interaction, which add extra error to the measured value. Several studies were carried out in order to determine the magnitude of these errors due to several parameters by using different instruments.

This study investigates the determination of a correction equation for the error in the reflectorless distance measurements that occurred outdoors in a distance of 100m due to the change of the incident angle of the laser beam. Three advanced total stations, 23 materials and 13 different incident angles are participated in the experiment for the data collection. Deviations up to 5cm are registered. Numerous of approximation equations are tested in order to estimate, which describes better the distance deviation from the correct value. The RMSE and R2 are used as criteria in order to ensure the reliability of the adaptations. It was fount that each total station has a different behavior with regard to the provided data. Thus one general correction equation of 2nd order became possible to determine, for each total station and for all the involved materials, which corrects all the measurements by an accuracy of ±3mm. Moreover individual equations of 1st, 2nd , 3rd and exponential order are determined for each material. The results certify that it is feasible the modeling of the deviations of the reflectorless distance measurement due to the beam’s incident angle and then for other influencing parameters. This fact strengthens the possibility to incorporate such equations in total stations’ software in order to automatically correct their reflectorless distance measurements.

A convenient procedure for the calibration and check of GNSS systems by using the relative static positioning method

Evangelia Lambrou, Nikolaos Kanellopoulos

Recent development in the area of GNSS-based measurements consists of combination of methodologies and modern manufactured antennas and receivers, which are able to provide coordinates of sub-centimeter accuracy. In order to succeed this, it is necessary that the measurement system (base and rover antennas- receivers and their ancillary equipment) to be calibrated and functioning properly, as the manufacturer defines. Therefore a full methodology that ensures the proper function of GNSS systems is indispensable. This paper describes a convenient procedure for the calibration and check of GNSS systems, using the relative static positioning method. Each one of the calibration or the check procedure can be applied individually. The appropriate statistical checks were carried out in both procedures in order to conclude with reliability about the proper function of the systems being checked. The methodology succeeds the results by using efficient number and type of observations and simple mathematical models. So it is convenient to be used by professionals in order to improve and to ensure their products. More over it could be a new supplement of the ISO 17123-8, which deals only with the real time kinematic method and informs the user only for the precision of the base system which is being checked and not about the accuracy of the measurements. An external control base of 2km length is used for the data acquisition. The control base is located at an optimum position in order to minimize the errors due to the elevation variance, the multipath effect and atmospheric conditions. Also the appropriate series of measurements are carried out in order to take into consideration the change of the satellite geometry. Consequently the proposed procedure provides an over all illustration about the status of the checked GNSS systems under any random environmental conditions. This estimation interests every professional in order to ensure the reliability of his products. Moreover it concludes not only about the precision of GNSS systems under check but also about the accuracy that they provide by the comparison to the ″ true″ values of the measured parameters.

Precise local Geoid definition. Case Study: Nisyros Island in Greece

EVANGELIA LAMBROU

The global geoid model EGM08 consists nowadays one of the best tools for the transformation of geometric heights provided by GNSS measurements to orthometric ones. Nevertheless there are some areas worldwide, where due to the strong variations of the terrain (high mountains, spread islands etc.), there is not a satisfied adaptation of the EGM08.

However the determination of accurate orthometric heights is required by demanding infrastructure and monitoring projects.

Moreover the need for unification of the vertical datums between islands and mainland in Greece as well as between adjacent countries arises as one of the major problems of the geodetic community.

Thus, the well spread use of GNSS needs a perfect geoid correction equation in order to derive reliable orthometric height from the geoidal ones by accuracy of cm level. This demands accurate and reliable knowledge of both heights at the examined area. The ellipsoidal heights are easily resulted by GNSS measurements, while the orthometric ones are extremely demanding in time and staff in order to be collected by some mm accuracy.

This study applies a direct measurement procedure and assesses, in terms of time and cost, the calculation of a precise local geoid at an insular part of Greece in order to achieve some mm accuracy.

The experimental application is implemented on Nisyros island. Nisyros Island is located at the southeast edge of the Aegean Sea. GNSS measurements by the relative static positioning method and orthometric height differences measurements by the Accurate Trigonometric Heighting method were carried out, connecting the established benchmarks. The orthometric and geometric heights of each benchmark were determined with ±6mm and ±10mm respectively by applying least square adjustments. The appropriate best adapting equation is determined as well as the contour lines of the derived local geoid undulation are drawn. Additionally the corresponding values of the geoid undulation N were calculated by the EGM08 geoid model. Thus, a new correction equation was formed in order to be more feasible for the concrete area. Moreover the zero-level geopotential value (Wo) of the island, has been determined and compared to the corresponding one of the neighboring to Nisyros Hellenic islands and the Greek Vertical Datum (GVD).

Knowingly orientation of Ancient Greek Temples

Pantazis George, Lambrou Evangelia

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.

Structural Health Monitoring of the Holy Aedicule in Jerusalem

Moropoulou Antonia, Karoglou Maria, Agapakis Ioannis, Mouzakis Charalampos, Simos Asimakopoulos, Pantazis George, Lambrou Evangelia

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.

Position determination of encoded and uncoded targets on the large hadron collider at Cern

S. Lapardhaja, E. Lambrou

The automatic detection of a great number of points of interest provides to photogrammetry essential capabilities for the automation of the procedure as well as for achieving optimum target position determination. The article deals with the use of image processing techniques in 2D images, which contribute to the detection of the targets, the ellipse fitting based on the least squares adjustment for the position determination of the targets, the decoding of encoded targets and the usage of collinearity equations combined with least squares in order to find the homologous points among several images for the uncoded targets

1 Accuracy in the determination of vertical displacements using Trigonometric Levelling and precision theodolites.
Τech. Chron. Α 1993, Vol.13, No 3, p.p. 273-281
2 Determination and setting up of the basic reference axis of a submarine by geodetic methodology,
Τech. Chron. Ι 1999, Vol.19, No 3, p.p. 103 - 111
3 Fast and accurate determination of astronomical coordinates Φ, Λ and azimuth, using a total station and GPS receiver.
Survey Review, Vol 37, No290, October 2003, p.p. 269 - 275
4 Accurate determination of the geoidal undulation N.
Reports on Geodesy, Warsaw University of Technology, Institute of Geodesy and Geodetic Astronomy, Νο1(64), 2003, p.p. 165 - 172. Presentation on "EGS – AGU – EUG Joint Assembly 2003", Nice – France
5 A standard network to control GPS receivers.
Reports on Geodesy, Warsaw University of Technology, Institute of Geodesy and Geodetic Astronomy, Νο 2 (69), 2004, p.p. 261-269. Presentation on "EGU 1st General Assembly 2004", Nice – France, 2004
6 Astrogeodetic study of the orientation of Ancient and Byzantine Monuments: Methodology and first results.
Journal of Astronomical History and Heritage. Volume 7 No 2, Number 14, p.p. 74-80, December 2004
7 On the date of early Christian Basilicas (Central Greece).
Mediterranean Archaeology and Archaeometry, issue 3/2007, Volume 6, p.p. 53-60. Presentation on "International Conference on Archaeοastronomy 14th SEAC 2006", Rhodos, April 2006
8 Accurate height difference determination using reflectorless total stations.
Tech. Chron. Sci. J. TCG, I, No 1-2, 2007
9 Astronomical azimuth determination by the hour angle of Polaris using ordinary total stations.
Survey Review, Vol. 40, No. 308, April 2008, p.p. 164-172
10 The orientation of Delos’ monuments.
Mediteranian Archaeology and Archaeometry, Vol. 9, No 1, 2009, pp 55-68 (indexed and abstracted in Arts and Humanities Citation Index Thomson USA)
11 Investigating the orientation of eleven mosques in Greece.
Journal of Astronomical History and Heritage, Vol.12, July 2009, pp 159-166
12 Evaluation of the Credibility of Reflectorless distance measurement.
Journal of Surveying Engineering, Vol.136,No.4, November 2010, pp 165-171
13 Special marking of 3d networks’ points for the monitoring of modern constructions.
Journal of Civil engineering and Architecture (ISSN 1934-7359), July 2011, Volume 5, Number 7, Serial No 44, pp 643-649.
Presentation on "13th FIG Symposium on Deformation measurements and Analysis – Measuring the changes - 4th IAG symposium on Geodesy for Geotechnical and Structural Engineering", Lisbon, Portugal, May 2008
14 Accurate Geoid height differences computation from GNSS data and modern astrogeodetic observations.
Proc. of the International Symposium on Gravity, Geoid and Height Systems (GGHS2012), U Marti (Ed.), IAG Symp. 141, pp 163-170, 2015.
Presentation on "International Symposium on Gravity, Geoid and Height Systems GGHS2012", Venice, Italy, October 2012
15 Analysis of the errors of the antenna’s set up at the GNSS measurements.
Journal of Civil engineering and Architecture (ISSN 1934-7359) Volume 7, No. 10 (Serial No. 71), pp. 1279-1286, October 2013
16 Remote Survey. An Alternative Method for Capturing Data.
Journal of Surveying Engineering, Volume 140, Issue 1, pp 60-64, February 2014
http://dx.doi.org/10.1061/(ASCE)SU.1943-5428.0000115, June 2013
17 3D Digital Terrestrial Model Creation Using Image Assisted Total Station and Rapid Prototyping Technology
International Journal of Heritage in the Digital Era, vol. 2, No 2, pp 245-262, September 2013
18 Estimation of the gauging and the calibration time interval for the modern total stations.
Journal of Civil Engineering and Architecture 9 1210-1216, pp 1210-1216
DOI:10.17265/1934-7359/2015.10.009, October 2015
19 Testing and performance evaluation of terrestrial panoramic imaging system in close range documentations.
International Journal of Engineering and Innovative Technology, Volume 6, Issue 6, December 2016
20 Assessment of the Greek Vertical Datum – A case study in central Greece
International Association of Geodesy Symposia. Presentation on 1st Joint Commission 2 and IGFS Meeting International Symposium on Gravity, Geoid and Height Systems 2016, 2016
21 Beyond the boundaries of feasible engineering geological solutions: stability considerations of the spectacular Red Beach cliffs on Santorini Island, Greece.
Environmental Earth Sciences, Issue 15/2017, August, 2017
22 Five-Dimensional (5D) Modelling of the Holy Aedicule of the Church of the Holy Sepulchre Through an Innovative and Interdisciplinary Approach
Mixed Reality and Gamification for Cultural Heritage pp. 247-270, April 2017,
http://link.springer.com/chapter/10.1007%2F978-3-319-49607-8_9
23 Faithful Rehabilitation
Magazine of the American Society of Civil Engineers, Civil Engineering, November 2017
24 Detecting the Centring Error of Geodetic Instruments over a ground mark through a tribrach based optical plummet
Applied Geomatics, https://doi.org/10.1007/s12518-017-0197-8, Volume 9, Issue 4, pp 237–245, December 2017
25 Check and calibration οf a single GNSS receiver by using the VRS RTN positioning method
Measurement, Volume 117, Pages 221–225, March 2018
26 The Influence of Deployment Parameters on 2D Wireless Sensor Network by Using a Centroidal Voronoi Tessellation Based Algorithm
IJSER, Volume 9, Issue 2, February 2018
27 Modeling the deviations of the Reflectorless Distance measurement due to the beam’s incident angle
International Journal of Applied Science and Technology, Vol. 8 No. 1, March 2018
28 A convenient procedure for the calibration and check of GNSS systems by using the relative static positioning method
International Journal of Scientific and Engineering Research, vol 9, issue 3, March 2018
29 Precise local Geoid definition. Case Study: Nisyros Island in Greece
International Journal of Engineering Technology and Scientific Innovation, Volume 3 Issue 2, Paper ID- ETS070381, April 2018
30 Knowingly orientation of Ancient Greek Temples
Annals of Archaeology Volume 1, Issue 2, 2018, PP 21-28 ISSN:2639-3662, 2018
31 Structural Health Monitoring of the Holy Aedicule in Jerusalem
Structural Control and Health Monitoring, DOI: 10.1002/stc.2387, 2019
32 Position determination of encoded and uncoded targets on the large hadron collider at Cern
Applied Geomatics, https://doi.org/10.1007/s12518-019-00274-7, 2019
1 The astronomical orientation and dating of Samos’ Heraion by using astrogeodetic method.
ΑΤΜ (scientific topics), issue 179, August – September 2006, pp. 40-45, 2006
2 Determination of astronomical latitude by using autocallibration.
Honorary Volume for Dr. Vlacho, ΤΑΤΜ, AUTH, 2011

The significance of 3D network adjustment by using different least squares methods for the constructions’ monitoring. Application on the monitoring network of the Holy Aedicule in Jerusalem.

Dimitrios Zachos, George Pantazis, Evangelia Lambrou

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.

Distance Limitations when using CORS Networks and GNSS Receivers for Deformation Monitoring.

Nikolaos Kanellopoulos, George Pantazis, Evangelia Lambrou

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.

A methodology for correcting refraction in vertical angles for precise monitoring in tunnels.

Konstantinos Nikolitsas, Evangelia Lambrou

During the last three decades, the possibility of the high-precision instruments has been offered to the geodetic community by the technological development. Despite of this advantage some crucial parameters affect their performance. One of these parameters is the refraction.

The geodetic refraction mainly affects the zenith (vertical) angle measurements, especially in tunnels and underground facilities, where high accuracy is needed for the monitoring of the deformations. The term atmospheric or geodetic refraction, is found in the relevant surveying literature as a mean to describe the alteration in the direction of the light curve as it propagates through the different layers of the lower part of the Earth's atmosphere.

In this present work, a new methodology is analyzed in order to eliminate the influence of the geodetic refraction in the zenith angle measurements. The main idea is the accurate measurement of the air temperature in different heights in order to calculate the temperature gradient at each position, where measurements of angles took place.

The application of the method took place through the analysis of the adjustment results of 3D geodetic network, which has been implemented in the TT1 tunnel at CERN. The choice of this test field is connected with the existence of seven Hydrostatic Levelling Systems (HLS) in the TT1 tunnel. These systems can provide height differences which are unaffected by the refraction with accuracy of ±10 μm. This choice permits the check of the results.

Finally, after the analysis of the results the new methodology is proved to be adequate for such accurate measurements since the standard deviation of the zenith angles residuals in 3D network adjustment is reduced approximately 70% after the refraction corrections and approaches the specifications of laser tracker (±1.5cc). Additionally, the maximum difference between the nominal height differences of HLSystems and the calculated height differences after the 3D network adjustment with the corrected zenith angles is very promising and approaches the value of 50μm.

Ιnvestigation of the Optimum Minimum Input Data For the Forecasting of 3D Point Position Changing, Using Non-Linear Autoregressive Neural Networks.

Alevizakou Eleni-Georgia, Evangelia Lambrou

One of the most attractive and popular intelligent technique in the scientific community, lately, is the Artificial Neural Networks (ANNs). They have been globally used in most disciplines (e.g., Economics, Medicine, Engineering) in order to solve difficult and complex problems neither as a new method nor as a complementary, more effective one. As it was expected, ANNs have been also introduced in numerous geodetic fields such as regional mapping of the Geoid, sea level forecasting, coordinate transformation, deformation monitoring etc. As far as the deformation monitoring is concerned ANNs have recently been used in the position changing forecast problem. In particular, a methodology, based on Non-Linear Autoregressive (NAR) and non-linear autoregressive with eXogenous inputs (NARX) Neural Networks, has been developed in order to provide forecasts for point position changing. Α question that emerged applying this methodology was the investigation of the optimum minimum number of available input data. The research reported in this paper aims to investigate this number, so that the produced short-term and long-term forecasts would have acceptable Mean Absolute Error (MAE), depending on the order of the individual position changing. The idea behind this research is mainly based on the probability of lack of access to big data. Experiments with different number of daily continuous data from GNSS permanent stations, starting from 3190 daily records, were carried out. Results reveal that the number of inputs plays an important but not crucial role during implementation of the methodology. It was concluded that reliable forecasts could indeed be produced using smaller number of input data.

1 Dam deformations monitoring by using Deodeti methods.
Presentation on "1st Panhellenic Conference of big dams with international participation", Larissa, November 2008. Symposium Proceedings.
2 Geodetic monitoring of bridge oscillations
Presentation on International conference "Innovations on Bridges and Soil-Bridge Interaction", Athens, October 2011. Symposium Proceedings, p.p 455 – 462.
3 A new method to check the angle precision of total stations.
Presentation on FIG Working Week 2015, From the Wisdom of the Ages to the Challenges of the Modern World", Sofia, Bulgaria, May 2015. Symposium Proceedings.
4 The significance of 3D network adjustment by using different least squares methods for the constructions’ monitoring. Application on the monitoring network of the Holy Aedicule in Jerusalem.
Presentation on 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
5 Distance Limitations when using CORS Networks and GNSS Receivers for Deformation Monitoring.
Presentation on 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
6 A methodology for correcting refraction in vertical angles for precise monitoring in tunnels.
Presentation on 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
7 Ιnvestigation of the Optimum Minimum Input Data For the Forecasting of 3D Point Position Changing, Using Non-Linear Autoregressive Neural Networks.
Presentation on 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.

Errors in the determination of vertical displacements using Trigonometric Levelling

IOANNIS GOUGKOUTOUDIS, EVANGELIA LAMBROU, GEORGE PANTAZIS

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.

Enhancement of 3D monitoring networks’ sensitivity by low cost innovative implementation

Pantazis G., Lambrou E.

Usually 3D monitoring networks are used for long time due to the need for several campaigns of measurements’ acquisition, in concrete time intervals. Thus, the repeated instrumentation (total stations, targets or GNSS receivers) setting on specific networks’ points causes centering errors, which influences the points’ coordinates calculation and their uncertainty.

In order to obtain precise - forced centering, permanent, heavy and expensive pillar construction is needed. Although these pillars are appropriate cause not-reverse intervention to the construction’s site. For these reasons in many cases the establishment of pillars is not allowed or preferred. This work presents a flexible solution to the above mentioned problem. A prototype way for marking network’s points is being implied which assures forced unique instrument’s centering less than 0.1mm. A special Portable Metallic Pillar (PMP) was used for marking accessible points. This assists the enhancement of network’s sensitivity. It is light enough to carry, it accelerates and facilitates the centering and levelling of the instrumentation as well as it eliminates the time needed for the measurements. Additionally PMP is environment – friendly as it is invisible but for ever permanent.

Further a procedure for the accurate instrumentation’s height measurement is analyzed. PMPs were already used for the installation of the points of two 3D monitoring networks.

The first one was established at the streets around a modern football stadium, where 3 measurement campaigns were carried out within four years.

The second one was established at the site around a post-Byzantine Church, where 4 measurement campaigns were carried out in one year, as large displacements were observed.

The measurements analysis proved a satisfied networks’ sensitivity and points out the contribution, the convenience and the usefulness of the PMPs in such applications.

Merging geometric documentation with materials characterization and analysis of the history of the Holy Aedicule in the church of the Holy Sepulchre in Jerusalem

A. Georgopoulos, E. Lambrou, G. Pantazis, P. Agrafiotis, K. Lampropoulos, E. Delegou, M. Apostolopoulou, M. Alexakis, A. Moropoulou

The National Technical University of Athens, after invitation from His All Holiness, Beatitude Patriarch of Jerusalem and All Palestine, Theophilos III, signed a programmatic agreement with the Jerusalem Patriarchate and implemented an Integrated Diagnostic Research Project and Strategic Planning for Materials, Interventions Conservation and Rehabilitation of the Holy Aedicule of the Church of the Holy Sepulchre in Jerusalem. Within this framework, the Scientific Coordinator headed an interdisciplinary Research Group comprised of Architects, Chemical Engineers, Geomatics Surveying Engineers and Civil Engineers of NTUA. This paper will focus on 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. This combined analysis elucidates the construction phases and the hidden historical information behind the contemporary structure, which significantly affects its current state of preservation and forms the basis for the development and implementation of the conservation, reinforcement and repair interventions that are scheduled to be completed by March 2017.

Specifically, the geometric documentation produced an accurate three-dimensional (3D) model with the use of photogrammetric and geodetic methods, both for the interior and the exterior of the Holy Aedicule through images and scanned data collection for the reconstruction of the model in actual scale. This was realized via data processing (sorting of images, orientation, export 3D cloud points, dense point cloud processing, creation of surfaces and grouping them), for reconstructing 3D scenes of increased reliability and high accuracy. From this 3D model the production of sections at specific positions was also possible, supported by suitable geodetic measurements. In addition, accurate measurements were performed in order to assess the verticality of structural elements, like the iron girder set up by the British in 1947 and some of the pillars of the monument.

This work, thus, demonstrated that adopting an interdisciplinary approach for documentation can emerge as a powerful tool for a better understanding of monuments, both in terms.

Holy Selphuchre Monitoring System

Moropoulou Antonia, Karoglou Maria, Agapakis Ioannis, Mouzakis Charalambos, Asimakopoulos Simos, Pantazis George, Lambrou Evangelia

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 temperature 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 influence 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 recorded 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 continuous 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.

A methodology for WSN deployment in 2D large-scale constraining environments, using computational geometry algorithms.

Athanasios Iliodromitis, Georgios Pantazis, Vassilios Vescoukis, Evangelia Lambrou

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.

Investigation of the dependence between digital height readings and the meteorological parameters by using a stand-alone set up and repeatable short term measurements.

nastasios-Grammatas Kampouris, Evangelia Lambrou, George Pantazis

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.

Monitoring applications by using the Remote Survey Method.

Charalampos Molyvas, Evangelia Lambrou

In 2014 a methodology of Remote Survey was introduced. This methodology is a combination of instrumentation, software and means of communication, which allows surveyor to sight and measure, without having to be at the designated site. This successful experiment took place in the laboratories of the NTUA, where the surveyor managed to operate an Image Assisted Total Station (IATS), using two intermediate devices (PCs) and an internet connection, with acceptable results, according to the ISO17123-3 procedure. The goal of this paper is the presentation of implementing the methodology of Remote Survey for constructions monitoring. For this purpose an IATS will be placed on the appropriate monitoring position at the construction by using internet connection via WiFi network. Also, it will be essential to synchronize the internal clock of the IATS with the global time servers and to report automatically the real time of the observation, which by default is different than the one when the surveyor gives the command via the PC in office. The most important advantage of this methodology is the fact that free software mid cost instrumentation combined with common wireless connection and low cost PCs can provide to the engineers the potential to obtain the remote control and handling of a total station without any additional costs. The pros and cons of this attempt are presented and further discussion is presented in how this methodology can be implemented.

Multispectral monitoring of the successive phases of the Holy Aedicule rehabilitation.

Antonia Moropoulou, Andreas Georgopoulos, Evangelia Lambrou, George Pantazis, Sofia Soile, Sevasti Tapeinaki, Elisavet Tsilimantou, Kyriakos Lampropoulos

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.

1 Errors in the determination of vertical displacements using Trigonometric Levelling.
Presentation on "6th International FIG symposium on deformation measurements", Hannover, Germany, February 1992. Symposium Proceedings, p.p.270-284
2 Determination of the orientation of the "Meteora monastic community" churches by astrogeodetic methodology.
Presented at "1st Archeological Work of Thessaly and the Greek Mainland" , Volos, February 2003, pages 14, Symposium Proceedings
3 Documentation and presentation of very steep and rocky ground surfaces by geodetic methods.
Presented at "11th International FIG symposium on deformation measurements", Santorini May 2003. Symposium Proceedings, p.p. 225 – 231
4 Researching the orientation of monuments. Τhe church of the Great Meteoro monastery
Presented at "XIX International Symposium CIPA 2003, New perspectives to save Cultural Heritage", Antalya - Turkey, October 2003 Symposium Proceedings p.p. 635 - 638
5 A geodetic network solution through combination of gps and terrestrial observations
Presented at International Symposium της FIG, "Modern technologies, education and professional practice in the globalizing world", Sofia – Bulgaria, November 2003. Symposium Proceedings p.p. 182 - 188
6 Accurate orientation of the gyroscopes calibration system
Presented at "FIG Working Week 2004 – The Olympic Spirit in Surveying", Athens, May 2004, Symposium Proceedings (CD)
7 Geometric documentation of structures after an earthquake
Presented at "FIG Working Week 2004 – The Olympic Spirit in Surveying", Athens, May 2004, Symposium Proceedings (CD)
8 Investigation on the orientation of the mosques in Ioannina by astrogeodetic methodology.
Presented at 4th Interdisciplinary Conference of NTUA and M.I.R.C, Athens 2007
9 Laboratorial tests of digital theodolites
Presented at International Symposium της FIG, "Modern technologies, education and professional practice in Geodesy and related fields", Sofia – Bulgaria, November 2004, Symposium Proceedings p.p. 72 – 79
10 Fast and accurate measurements of directions by using digital theodolites
Presented at International Symposium της FIG, "Modern technologies, education and professional practice in Geodesy and related fields", Sofia – Bulgaria, November 2004, Symposium Proceedings p.p. 63 – 71.
11 Τesting a laser scanner in comparison with a specific total station in Land Surveys
Presented at, "7th Conference on Optical 3-D Measurement Techniques", Vienna – Austria, October 2005, Symposium Proceedings p.p. 93 – 102
12 Local geoid modelling via the geometric interpolation method
Presented at International Symposium της FIG, "Modern technologies, education and professional practice in Geodesy and related fields", Sofia – Bulgaria, November 2005. Symposium Proceedings p.p. 40 – 47
13 The dating of the Candlemas church at Meteora
Presented at "2nd archaeological work of Thessaly and Sterea Hellas 2003-2005, from prehistoric to modern times", Volos, March 2006,Symposium Proceedings Volume I, p.p. 539 - 550
14 A new geodetic methodology for the accurate documentation and monitoring of inaccessible surfaces
Presented at 3rd IAG symposium on Geodesy for Geotechnical and Structural Engineering and 12th International FIG symposium on deformation measurements", Baden, Austria, May 2006, Symposium Proceedings (CD).
15 The relationship between uncertainty of measurement and uncertainty in geodetic applications.
Presented at "2nd Regular National Congress of Metrology, Thessaloniki, October 2007 Symposium Proceedings (CD)
16 Necessity to create certification standards for geodetic metrics.
Presented at "2nd Regular National Congress of Metrology, Thessaloniki, October 2007 Symposium Proceedings (CD)
17 A convenient method for accurate Height differences determination
Παρουσίαση στο "17th International Symposium on Modern technologies, education and professional practice in Geodesy and related fields", Sofia, Bulgaria, November 2007, Symposium Proceedings p.p. 45-53
18 Evaluation of the International Standard ISO 17123-5
Presented at "3rd Regular National Congress of Metrology", Larnaca, Cyprus, February 2010, Symposium Proceedings
19 Proposal for the calibration method of the digital camera of anImage Assisted Total Stations (IATS)
Presented at "3rd Regular National Congress of Metrology", Larnaca, Cyprus, February 2010, Symposium Proceedings
20 Using geodetic and laser scanner measurements for measuring and monitoring the structural damage of a post-byzantine church
Presented at "8th International Symposium on the Conservation of Monuments in the Mediterranean Basin. Monument Damage Hazards & Rehabilitation Technologies", Patra, May – June 2010, Symposium Proceedings
21 Fast and Convenient Determination of Geoid Undulation N in an Urban Area
Presented at FIG Working Week 2011, Bridging the Gap between Cultures", Marrakech, Morocco, May 2011. Symposium Proceedings
22 Estimation of the gauging and the calibration time interval for the modern total stations
Presented at "4th Regular National Congress of Metrology, Athens, February 2012, Symposium Proceedings
23 Detecting the uncertainty in the reading of a directions system
Presented at "4th Regular National Congress of Metrology ", Athens, February 2012, Symposium Proceedings
24 Optimization of a vertical network by adjument’s simulations
Presented at "5th Regular National Congress of Metrology ",Athens May 2014, Symposium Proceedings
25 Enhancement of 3D monitoring networks’ sensitivity by low cost innovative implementation
Presented at "3rd Joint International Symposium on Deformation Monitoring (JISDM)", Vienna , Austria, March 2016. Symposium Proceedings. Post to the e-journal mycoordinates. Volume XIII, Issue 1, January 2017
26 The standard external checking and calibration field for total stations
Presented at "6th Regular National Congress of Metrology ", Athens May 2016, Symposium Proceedings
27 An engineering geological assessment using terrestrial laser scanning for the stabilization of a volcanic slope in Santorini island
Presented at "14th International Conference of the Hellenic Geological Society", Thessaloniki, Μay 2016. Published in the Release of the Hellenic Geological Society, Volume L, p.p. 835-844
28 Merging geometric documentation with materials characterization and analysis of the history of the Holy Aedicule in the church of the Holy Sepulchre in Jerusalem
Presented at " GEOMATICS & RESTORATION - Conservation of Cultural Heritage in the Digital Era” conference, Florence", May 2017, Symposium Proceedings
29 Total stations integraded calibration methodology for distance measurements at external baseline
Presented at "7th Regular National Congress of Metrology ", Athens May 2018, Symposium Proceedings
30 Holy Selphuchre Monitoring System
Presented at "1st International Conference on "Transdisciplinary Multispectral Modeling and Cooperation for the Preservation of Cultural Heritage (TMM_CH)", Athens, October 2018, Symposium Proceedings
31 A methodology for WSN deployment in 2D large-scale constraining environments, using computational geometry algorithms.
Presented at 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
32 Investigation of the dependence between digital height readings and the meteorological parameters by using a stand-alone set up and repeatable short term measurements.
Presented at 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
33 Monitoring applications by using the Remote Survey Method.
Presented at 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
34 Multispectral monitoring of the successive phases of the Holy Aedicule rehabilitation.
Presented at 4th Joint International Symposium on Deformation Monitoring (JISDM), Aθήνα, Ελλάδα, Μάιος 2019.
1 The evolution of the conventional terrestrial geodetic instruments of the 20th century in Greece
Presented at the symposium "The revolution of the instruments, the methods and the measurement systems of the Survey sciences in Greece", Thessaloniki, April 2005, Symposium Proceedings
2 The contribution of the geodetic instruments and computer evolution on education at the School of Rural and Surveying Engineering of NTUA on the subject of cadastral surveys
Presented at the symposium "The revolution of the instruments, the methods and the measurement systems of the Survey sciences in Greece", Thessaloniki, April 2005, Symposium Proceedings
3 Proposal for the creation of a modern and accurate map of the geoid in Greece
4 The evolution of terrestrial conventional geodetic technology and the need to change its certification standard
5 Determination of the deformation-strength of structures by the controlled loading method, in real time
6 3.8.6 The contribution of a modern geodetic methodology in the investigation of the astronomical orientation of monuments and in their dating.
Presentation of complete studies applied to monuments in Greek area (Classical temples, early Christian basilicas, Byzantine churches)
7 Geodetic distance measurement systems and their contribution to the Topography Engineer's Science
8 The contribution of surveying engeneers in high precision projects the case of the European Organization for Nuclear Research (CERN)
9 Monitoring of the kinematic behaviour of the Holy Aedicule of the Holy Sepulcher in Jerusalem during the rehabilitation works