C. Loupasakis, P. Tsangaratos, D. Rozos, Th. Rondoyianni, A. Vafidis, G. Kritikakis, M. Steiakakis, Z. Agioutantis, A. Savvaidis, P. Soupios, I. Papadopoulos, N. Papadopoulos, A. Sarris, M.-D. Mangriotis, U. Dikmen
The specification of the near surface ground conditions is highly important for the design of civil constructions. These conditions determine primarily the ability of the foundation formations to bear loads, the stress – strain relations and the corresponding settlements, as well as the soil amplification and corresponding peak ground motion in case of dynamic loading. The static and dynamic geotechnical parameters as well as the ground-type/soil-category can be determined by combining geotechnical and geophysical methods, such as engineering geological surface mapping, geotechnical drilling, in situ and laboratory testing and geophysical investigations. The above mentioned methods were combined, through the Thalis ″Geo-Characterization″ project, for the site characterization in selected sites of the Hellenic Accelerometric Network (HAN) in the area of Crete Island. The combination of the geotechnical and geophysical methods in thirteen (13) sites provided sufficient information about their limitations, setting up the minimum tests requirements in relation to the type of the geological formations. The reduced accuracy of the surface mapping in urban sites, the uncertainties introduced by the geophysical survey in sites with complex geology and the 1D data provided by the geotechnical drills are some of the causes affecting the right order and the quantity of the necessary investigation methods. Through this study the gradual improvement on the accuracy of site characterization data is going to be presented by providing characteristic examples from a total number of thirteen sites. Selected examples present sufficiently the ability, the limitations and the right order of the investigation methods.
The olive-oil industry is one of the most important sectors of agricultural production in Greece, which is the third in olive-oil production country worldwide. Olive oil mill wastes (OOMW) constitute a major factor in pollution in olivegrowing regions and an important problem to be solved for the agricultural industry. The olive-oil mill wastes are normally deposited at tanks, or directly in the soil or even on adjacent torrents, rivers and lakes posing a high risk to the environmental pollution and the community health. GEODIAMETRIS project aspires to develop integrated geoinformatic methodologies for performing monitoring of land pollution from the disposal of OOMW in the island of Crete -Greece. These methodologies integrate GPS surveys, satellite remote sensing and risk assessment analysis in GIS environment, application of in situ and laboratory geophysical methodologies as well as soil and water physicochemical analysis. Concerning project’s preliminary results, all the operating OOMW areas located in Crete have been already registered through extensive GPS field campaigns. Their spatial and attribute information has been stored in an integrated GIS database and an overall OOMW spectral signature database has been constructed through the analysis of multi-temporal Landsat-8 OLI satellite images. In addition, a specific OOMW area located in Alikianos village (Chania–Crete) has been selected as one of the main case study areas. Various geophysical methodologies, such as Electrical Resistivity Tomography, Induced Polarization, multifrequency electromagnetic, Self Potential measurements and Ground Penetrating Radar have been already implemented. Soil as well as liquid samples have been collected for performing physico-chemical analysis. The preliminary results have already contributed to the gradual development of an integrated environmental monitoring tool for studying and understanding environmental degradation from the disposal of OOMW.
It is estimated that more than 20,000 natural lakes are found across China. Most of these lakes are undergoing eutrophication or other severe environmental nuisances owing to natural and/or anthropogenic processes. In order to prevent or to minimize such damaging impacts, and to ascertain a proper quality management of the lake water and the associated fish resources, it is required to have access to up-to-date, accurate, and relevant data and information on the aquatic ecosystem in a timely manner. The “Dragon 3” project, supported by the European Space Agency, is focusing on Xin’an river watershed and investigates the impact of water quality and land cover/use change on the spatio-temporal distribution of the fishing grounds in Qiandao Lake. In this paper, the land use changes derived from satellite images is presented. Initially, Landsat 5 TM and Landsat 8 LDCM have been analyzed for the last 20 years in the vicinity of the Xin’an river watershed. Following the radiometric calibration of the images, several pixel-base classification algorithms have been evaluated including Spectral Angle Mapper (SAM), Support Vector Machine (SVM) as well Neural Network (NN). As it was found using the multi-temporal satellite imagery, the SVM algorithm was able to give high kappa accuracy estimated at around 0.90. In addition EO-Hyperion images over the western part of the Xin’an River were evaluated using hyperspectral vegetation indices as well using linear spectral un-mixing techniques. In addition, ENVISAT radar images have been evaluated in terms of land use change. The final outcomes indicate a significant urban expansion in the surrounding area of the Xin’an River which impacts the water quality investigation. Finally, a Landsat image was processed in order to estimate the Trophic State Index (TSI) values over the water bodies and the highest values were observed over the Xin’an river watershed and more specifically for the urban sites.
Olive oil mills’ wastes (OOMW) are one of the byproducts of the oil production that can lead to serious environmental pollution when they are deposited in ponds dug on the ground surface. Electrical Resistivity Tomography (ERT) method can provide a valuable tool in order to monitor through time the physical flow of the wastes into the subsurface. ERT could potentially locate the electrical signature due to lower resistivity values resulting from the leakage of OOMW to the subsurface. For this purpose, two vertical boreholes were installed (12m depth, 9 m apart) in the vicinity of an existing pond which is filled with OOMW during the oil production period. The test site is situated in Saint Andreas village about 15km south of the city of Rethymno (Crete, Greece). Surface ERT measurements were collected along multiple lines in order to reconstruct the subsurface resistivity models. Data acquisition was performed with standard and optimized electrode configuration protocols. The monitoring survey includes the ERT data collection for a period of time. The study was initiated before the OOMW were deposited in the pond, so resistivity fluctuations are expected due to the flow of OOMW in the porous subsurface media through time. Preliminary results show the good correlation of the ERT images with the drilled geological formations and the identification of low resistivity subsurface zone that could be attributed to the flow of the wastes within the porous layers.
KEYWORDS: Geographic information systems, Hazard analysis, Cultural heritage, Earthquakes, Data modeling, Remote sensing, Information fusion, Earth sciences, Roads, Environmental sensing
Natural hazards, such as earthquakes, can have a large destructive effect on cultural heritage sites
conservation. This study aims to assess from a geospatial perspective the risk from natural hazards for the
archaeological sites and monuments and evaluate the potential tectonic activity impact on the cultural and historic
heritage. Geomorphometric data derivatives that can be extracted from Digital Elevation Models (DEMs) provide
information relevant with active tectonics. The specific extracted tectonic information when being used on the basis of
analytical hierarchy process and weighted linear combination approach can offer an important robust approach. The
ranking of the derived information relatively to specific criteria of weights can enhance the interrelationships and
assemblages over neotectonics aspects. The outcomes of that methodological framework can propose an assessment
approach for the spatial distribution of neotectonic activity and can become a useful tool to assessing seismic hazard for
disaster risk reduction. The risk assessment aspects of such a hazard are being interlinked with the archaeological sites
in order to highlight and examine those that are exposed on ongoing tectonic activity and seismic hazard. Paphos area
in Cyprus has been used as the test bed for the particular analysis. The results show an important number of
archaeological sites being located within zones of high degree of neotectonic activity.
Vegetation indices have been widely used for the detection of archaeological traces, based on crop marks, during different phenological stages. Such indices can be used in order to enhance interpretation performance of multispectral and hyperspectral satellite data, for identification of buried archeological remains. Although a variety of indices exists in the literature, research is still limited and only a small group of these indices have been explored. This paper aims to highlight the prospects as well the limitations of several broadband vegetation indices for the detection of Neolithic tells in the Thessalian plain (Greece). Several multispectral Landsat 5 TM and Landsat 7 ETM+ satellite images have been used for evaluating the effectiveness of such indices. In addition, new developed algorithms and hyperspectral narrowband indices, specially designed for archaeological research, have been also used and compared using hyperspectral satellite data (EO-Hyperion). Indeed, the Normalized Archaeological Vegetation Index (NAVI) as well as a linear transformation of the Landsat 5 TM were applied to satellite data. The above were also compared to other processing algorithms such as Tasseled – Cap algorithm and Principal Component Analysis. The results have shown that several indices and new algorithms may be used for the enhancement of crop marks, while some no-widely used indices can be successfully used for archaeological purposes.
Satellite data can be used as a valuable tool for the detection of water pipeline leakages in semiarid areas. However the
use of multi-temporal satellite images for this purpose can be problematic since reflectance values may change due to
phenological changes of plants, radiometric errors during the pre-processing of satellite data, etc. It is therefore important
to establish a spectral signature library with “ground truth data” for different scenarios of water leakages in a control site
minimizing other potential errors. For this purpose, the GER 1500 spectroradiometer was used for measuring the
reflectance values of three different targets: soil, vegetation and asphalt. The targets were saturated with a specific
amount of water and then several spectroradiometric measurements were taken. The narrowband reflectance values were
then re-scaled to spectral bands of Landsat 5 TM and spectral signature variations were highlighted for all targets before
and after moisture level were increased. Using these data, threshold values were defined in order to be used for
multispectral satellite data analysis. Specifically, this data was used for detection of water leakages in pipelines in
Cyprus using Landsat 5 TM images,.
Air pollutants, together with climatic parameters, are of major importance for the deterioration of cultural heritage monuments. Atmospheric pollution is widely recognized as one of the major anthropogenic threats to architectural cultural heritage, in particular when associated with water absorption phenomena. Atmospheric particle deposition on surfaces of Monuments (of cultural heritage interest) may cause an aesthetic impact induced by a series of chemical reactions. Therefore there is a need for systematic monitoring and mapping of air pollution for areas where important archaeological sites and monuments are found. observation techniques, such as the use of satellite image for the retrieval of Aerosol Optical Thickness (AOT), are ideal for this purpose. In this paper, all important monuments of the Paphos District, listed by the Department of Antiquities of Cyprus, have been mapped using Geographical Information Systems. Several recent (2012) MODIS satellite images (both Aqua and Terra) have been used to extract the AOT values in this area. Multi-temporal analysis was performed to identify areas of high risk where AOT values are considered to be high. In situ observations have been also carried out to verify the results.
The city of Demetriada was constructed around 294-292 BC and became a stronghold of the Macedonian navy fleet, whereas in the Roman period it experienced significant growth and blossoming. The ancient theatre of the town was constructed at the same time with the foundation of the city, without being used for 2 centuries (1st ce. BC - 1st ce. A.D.) and being completely abandoned after the 4th ce. A.D., to be used only as a quarry for extraction of building material for Christian basilicas in the area. The theatre was found in 1809 and excavations took place in various years since 1907. Geophysical approaches were exploited recently in an effort to map the subsurface of the surrounding area of the theatre and help the reconstruction works of it. Magnetic gradiometry, Ground Penetrating Radar (GPR) and Electrical Resistivity Tomogrpahy (ERT) techniques were employed for mapping the area of the orchestra and the scene of the theatre, together with the area extending to the south of the theatre. A number of features were recognized by the magnetic techniques including older excavation trenches and the pilar of the stoa of the proscenium. The different occupation phases of the area have been manifested through the employment of tomographic and stratigraphic geophysical techniques like three-dimensional ERT and GPR. Architectural orthogonal structures aligned in a S-N direction have been correlated to the already excavated buildings of the ceramic workshop. The workshop seems to expand in a large section of the area which was probably constructed after the final abandonment of the theatre.
A. Savvaidis, B. Margaris, N. Theodoulidis, V. Lekidis, Ch. Karakostas, M.-D. Mangriotis, I. Kalogeras, S. Koutrakis, A. Vafidis, M. Steiakakis, Z. Agioutantis, D. Rozos, C. Loupasakis, Th. Rondoyanni, P. Tsangaratos, U. Dikmen, N. Papadopoulos, A. Sarris, P. Soupios, E. Kokkinou, I. Papadopoulos, M. Kouli, F. Vallianatos
For the seismic action estimation according to Eurocode (EC8) one has to characterize site conditions and suitably estimate soil amplification and corresponding peak ground motion for the site. For this reason, as specified, one has to define a design spectrum through the ground-type/soil-category (S), and the peak ground acceleration (PGA) of the reference return period (TNCR) for the corresponding seismic zone and for structural technical requirements chosen by the designer. Ground type is defined through geophysical/geotechnical parameters, i.e. (a) the average shear wave velocity up to 30 meters depth, (b) the Standard Penetration Test blow-count, and (c) the undrained shear strength of soil. Through the “GEO-CHARACTERIZATION” THALIS-PROJECT we combine different geophysical and geotechnical methods in order to more accurately define the ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in the area of Crete Island. More specifically in the present efforts, geological information shear wave velocity and attenuation model calculated from seismic surface geophysical measurements is used. Additionally we utilize the ground acceleration recorded through HAN from intermediate depth earthquakes in the broader area of South Aegean Sea. Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for selected sites. The resulting information are compared with the values defined for the corresponding EC8 spectrum for the seismic zone comprising the island of Crete. As a final outcome of this work we intend to propose regional normalized elastic spectra for seismic design of structures and urban development planning and compare them with Eurocode.
Remote sensing may be used for quick and cost effective detection and monitoring of water leakages, since traditional field survey methods for detection of water pipeline leakages are costly and time consuming. Vegetation indices are widely used by researchers for many applications. Among them, NDVI, RVI and SAVI are indices that can be used for pipeline leakage detection. In this study, the above vegetation indices were evaluated based on Landsat ETM+ multispectral images in a multi-temporal mode. The evaluation was performed in the semiarid environment in Cyprus, in order to detect the position of points/areas where water leakage occurs and to examine the accuracy of the vegetation indices in detecting such events. In addition, a low altitude system was used to record spectral differences before and after a leakage event. The results showed that there are leakage points that could be detected using satellite images due to the increasing and decreasing of the surrounding vegetation affected by the water leaked of the pipeline. Other characteristics such as the soil type and precipitation were also examined. Finally, the low altitude system highlighted the advantages of using such non contact techniques for monitoring water leakages.
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