Advanced spectro-bathymetric mapping of shallow seafloor using UAV imagery and deep learning techniques
Advanced spectro-bathymetric mapping of shallow seafloor using UAV imagery and deep learning techniques
Since 1996, the Laboratory of Geophysical - Satellite Remote Sensing & Archaeo-environment of the Institute for Mediterranean Studies (I.M.S.) / Foundation of Research & Technology (F.O.R.T.H.) has been active in the areas of Geophysical Prospection, Satellite Remote Sensing, Geographical Information Systems (GIS), 3D Reconstructions & VR and Archaeo-environment and has been widely recognized due to the quality of the services provided, the results of the research projects carried out and the training of students and professional archaeologists both in Greece and abroad.
The Laboratory employs the most modern techniques for accurate field measurements and has a technical support (hardware and software) that meets the needs of processing, analyzing and mapping geophysical and satellite data. It has more than 30 collaborations with universities and research institutes from Greece and abroad (Australia, Belgium, France, Italy, U.S.A., China, Cyprus, Sweden, Island, Lithuania, Hungary, Bulgaria, a.o). Its long term collaboration with the Ministry of Culture and other cultural and educational foundations has created a bridge of communication and trust. Its long term collaboration with the different sections of the Ministry of Culture and other cultural organizations has created a channel of reciprocal communication and trust. The continuing activities of the Lab led to the publication of Archaeo-Telepiskopika Nea in order to enhance communication with the scientific community and help the dissemination of the results of our research projects.
Since 1996, the Lab has completed more than 100 research projects. Services and collaborations of the Lab have been expanded to cover a large number of Greek and foreign institutes and other public and private organizations including the Technical University of Crete, the University of Crete, the University of Athens, the University of Ioannina, the University of Cyprus, the Hellenic Ministry of Culture (Divisions of Volos, Cyclades, Dodekanesse, Kavala, Komotini, Chania, Lasithi, Thebes, Lamia, Kerkyra, Ioannina, a.o.), ITSAK, Foundation of Hellenic World, Foundation for the Study of Alexander's Civilization, Natural History Museum - University of Crete, Municipality of Rethymno, Ecole Francaise D'Athenes, Swedish Archaeological School of Athens, K.I. Sarantopoulos Ltd - METON Ltd (Athens - Salonika highway), Instituto Per Gli Studi Micenei De Egeo-Anatolici, Groningen Inst. of Archaeology, Université Catholique de Louvain, Οhio State University, Univ. of Chicago, Univ. of Cornell, Univ. of Washington, Univ. of Nebraska - Lincoln, Univ. of Melbourne and Univ. of Monash, the Chinese Academy of Social Sciences, a.o. The Lab is also connected to development and public agencies for carrying out large scale development and construction works (e.g. construction of national road Athens-Thessaloniki, Attika highway, ERGOSE A.E. railways, AGET-HERAKLES, K.I. Sarantopoulos Ltd - ΜΕΤOΝ Ltd, ΤΕΑΒ Α.Ε., Doxiadis Associates/ABP PLUS International S.A., Prefecture of Rethymno, Municipality of Rethymno, a.o.).
Among the major milestones of the Lab, we can include the following:
Advanced spectro-bathymetric mapping of shallow seafloor using UAV imagery and deep learning techniques
Detect and Attribute agricultural droughts to Anthropogenic Climate Change
:The purpose of the proposed project is to establish an integrated spatial decision-making system in large-scale (Crete Water District) with the aim of: (a) precisely identifying irrigation needs, according to optimal crop yields and proper management of water resources; b) designing optimal adaptation scenarios for the agricultural sector in the light of upcoming climate change; and c) the dynamic integration of the above information through the creation of a platform for immediate and real-time updated information to be provided to businesses and entities, whose actions are directly related to the optimal design and management of land improvement projects in the Region of Crete.
In October 2019 the Ephorate of Underwater Antiquities in collaboration with the Laboratory of Geophysical Satellite Remote Sensing and Archaeoenvironment of IMS-FORTH undertook a scoping survey of the ancient harbour of Ierapetra (anc. Hierapytna) in Eastern Crete. The objective was to increase our understanding of the ancient harbour and its relationship with the present landscape. The survey examined the eastern mole, the modern harbour area and the western foreshore. The survey revealed a complex landscape, with changes over time that had not been previously noted and which affected the interpretation of the location and access to the ancient harbour. A series of previously unrecorded Roman structures were also identified.
Διαχρονικά τοπία πολιτισμού της Κρήτης: Αναδεικνύοντας τον θαλάσσιο και ορεινό πλούτο του Μιραμπέλου
The BIOnian project aims at identifying, recording, mapping and developing "smart" tools for monitoring and identifying the Ionian Islands Region species that are related, supported or used as habitat for the Region's territorial resources.
Rozos, D.; Margaris, B.; Theodoulidis, N.; Lekidis, V.; Karakostas, Ch.; Mangriotis, M-D.; Kalogeras, I.; Koutrakis, S.; Vafidis, A.; Steiakakis, M.; Agioutantis, Z.; Savvaidis, A.; Loupasakis, C.; Rondoyanni, Th.; Tsangaratos, P.; Dikmen, U.; Papadopoulos, N.; Sarris, A.; Soupios, P.; Kokkinou, E.; Papadopoulos, I.; Kouli, M.; Vallianatos, F., "Geo-characterization according to recent advances of Eurocode (EC8)", First International Conference on Remote Sensing and Geoinformation, 8-10 April, pp. 879513-879519.
Sarris, A.; Papadopoulos, N.; Agapiou, A.; Salvi, M. C.; Hadjimitsis, D. G.; Parkinson, W. A.; Yerkes, R. W.; Gyucha, A.; Duffy, P. R., "Integration of geophysical surveys, ground hyperspectral measurements, aerial and satellite imagery for archaeological prospection of prehistoric sites: the case study of Vésztő-Mágor Tell, Hungary", Journal of Archaeological Science, vol. 3, no. 40, pp. 1454-1470.
AutoGR-Toolkit version 3.5
AutoGR-Toolkit is a set of scripts to improve, facilitate and speedup the process of georeferencing images.
AutoGR-Toolkit, and the embedded tools (GGrab, AutoGR-SIFT, GeoRef-Filtering, GeoTiff-Converter and AutoGR-Photogrammetry) are distributed for free and can be redistributed (free of charge). It is recommended that users register and download the toolkit directly from the website www.ims.forth.gr/AutoGR. Which will allow for future contact, notifications, bug-fixes or updates if needed.
Allows you to save a georeferenced satellite image (for personal and research purpose) of the area of interest from WMS servers.
GGrab and GeoTiff Converter use the Geospatial Data Abstraction Library
Automatically produces ground control points for image georeferencing.
It is based on the automatic image matching "ASIFT" algorithm, produced by Jean-Michel Morel and Guoshen Yu (http://www.cmap.polytechnique.fr/~yu/research/ASIFT/demo.html) as an implementation of the David Lowe's SIFT algorithm (http://www.cs.ubc.ca/~lowe/keypoints).
It now implements OpenCV3 libraries for more efficient algorithms.
AutoGR-SIFT usually produces thousands of points in few seconds and this script lets you reduce this number to a more manageable one.
It extracts geographical information from a geotiff file and it produces a .jpg with its worldfile.
Using the global digital terrain model available online, this scripts provides you with the facilities to extract X, Y and Z coordinates for each location in the world. It also allows to generate Agisoft PhotoScan, VSFM and sfm_georef points for photogrammetric 3D models georeferencing in complete automation.
Thanks to Gribouillis and pyTony from the Daniweb's Python Forum and all beta-testers for their immeasurable support for the creation of some special functions in this software.
IMS-FORTH provided the facilities and technical support to develop and finalize this set of applications.
If you are running Windows Vista or you experience problems executing the program, try installing the Microsoft Visual C++ 2008 Redistributable Package (you can download it from the following link http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=29).
If the problem persists, feel free to contact the author of the program (see the email below) for assistance.
In case of problems, requests/whishlist or feedback, feel free to contact the author of AutoGR-Toolkit:
Gianluca Cantoro // gianluca.cantoro [at] gmail.com
Please also consider the dedicated google group for support related issues.
3-D Inversion of surface ERT Data
User's manual (pdf 1.8MB)
3DINV is a program for the three-dimensional (3-D) inversion of surface Electrical Resistivity Tomography (ERT) data in order to automatically determine a 3-D resistivity subsurface model. The program performs smoothness constrained (Occam's) inversion in order to address the non-uniqueness of the inverse problem and stabilize the procedure. The subsurface is divided in homogeneous and isotropic hexahedral elements and a 3-D Finite Element Modeling (FEM) routine is employed to calculate the resistivity response of 3-D bodies. The adjoint equation technique has been incorporated into the FEM scheme to calculate the Jacobian matrix. An iterative method (LSMR) is used to update the resistivity model though the inversion iterations.
This work was supported by ArchaeoLandscapes-ArcLand: Europe European multiannual project (2010-2015) - European Commission - Directorate General Education and Culture, Programme « Culture » (2007-2013). 2010-2015
For any problems or remarks on the program contact: Dr. Nikos Papadopoulos // nikos [at] ims.forth.gr
CataThumb (BKMF) version 1.6
This is a free software (distributed "AS IS") that will allow you to easily create an Excel file for cataloguing photo-sorties trough a windows GUI.
Its name comes from CATAlogue and THUMBnails (BKMF is an internal code and it was the first name of this software).
Given a folder with photos (JPG or NEF), CataThumb creates an XLS file with preview of photos, LatLong coordinate (if stored in the EXIF of the photos), Project name, flight date and keywords.
CataThumb will create also (only if coordinates are available) a KML file with a GPS track and photo previews.
In case of problems, requests/whishlist or feedback, feel free to contact the author of CataThumb: Gianluca Cantoro // gianluca.cantoro [at] gmail.com
Please also consider the dedicated google group for support related issues.
The new developments of satellite remote sensing and Geographical Information Systems have given a new dimension in archaeological research and the management of cultural resources. Innovative satellite sensors of high spatial and spectral resolution, along with the use of high accuracy Global Positioning (GPS) systems and enhanced image processing systems offer great possibilities in the mapping of archaeological sites. In addition, the combination of the above technologies with other databases which contain archaeological and environmental information and with socio-economic models has direct consequences on our knowledge of use of cultural space in antiquity as well as on management policies of archaeological sites today.
Satellite images are used for capturing the wider area of archaeological sites, offering the possibility of comparison and classification of multispectral information. Archaeological research incorporates satellite remote sensing aiming at: firstly the identification of environmental parameters and their association to the topography of archaeological monuments and secondly, the assessment of the spectral signatures of archaeological sites with the ultimate goal of developing predictive archaeological models. In this way, satellite remote sensing constitutes a method of archaeological information retrieval, without the use of excavation or intensive survey procedures.
Moving one step further, Geographical Information Systems could be used for integrating archaeological data, together with satellite and aerial images, topographic and geological maps and other digital environmental and cultural information. One of the most important applications of the Geographic Information Systems is the development of predictive models for archaeological site assessment based on image and statistical processing techniques of satellite imagery and environmental information. These methods are aiming to the management of cultural resources and the decision making process in large development works. Prediction models are based on the hypothesis that the spatial distribution of archaeological sites is a function of environmental parameters that exist in the specific region of interest. Avoiding high-risk areas, namely areas that have a large probability to contain archaeological sites, it is possible to insure the protection of monuments, a better planning of the development works and the proper accommodation of large amounts of funds.
The need to develop of a Geographic Information System of Cultural Resources, with capabilities of processing and modeling digital images, is actually imposed by the effort of accommodating funds, due to the high cost of surface surveying and archaeological site registration and assessment during or prior the course of large scale construction works (e.g. highway or railway construction, expansion of rural estates, exploitation of coastal areas, construction of waste dump areas, a.o.). The adoption of such a system has direct consequences in enhancing the current inventory systems and electronic databases and in upgrading the current models of protection and the general strategy of management of cultural resources. A further advantage of GIS lies in their ability of updating their geographical information index in a continuous and interactive mode, processing and storing large volume of diverse origin data and creating thematic maps based on specific inquiries. The above can be used in archaeological research for modeling the settlement patterns of a region, locating and outlining high probability archaeological candidate sites, studying the communication or defense networks, specifying cost surface regions used for the exploitation of natural resources, etc. The creation of electronic thematic maps that present various cultural and environmental information simultaneously, could be extremely useful in solving problems resulted by the environmental and development plans, suggesting specific solutions for the protection, preservation and management of ancient monuments.
The Laboratory of Geophysical-Satellite Remote Sensing & Archaeo-environment has been active in the above fields with a number of research projects in Amorgos (electronic archaeological map of Amorgos and study of the communication network between towers of the historical period), Mantineia (analysis of the defensive network of the wider Mantineia region and detection of new outposts), Itanos and Lasithi (development of a GIS for the management of archaeological monuments and the mapping of archaeological sites), Crete (study of the Minoan peak sanctuaries and modeling of cultural topography) and Palaipaphos-Cyprus (construction of the archaeological atlas of Palaipaphos). Similarly, one of the current projects of the Lab is dealing with the Development of an Expert System for the Monitoring, Management & Protection of the Natural Landscape & Environmental Resources of the Island of Crete (EMERIC).
Geographic Information Systems offer a unique mode of representing the ancient environment and its settlement patterns through the modeling of geomorphology and hydrology, viewshed analysis and statistical processing and correlation between natural and cultural variables. This type of approach should not remain static. Instead, it should be continuously transformed through a constant feedback and updating of geographic and cultural information, in order to meet the challenges generated by the increase of archaeological information, the extreme environmental pressures (desertification, erosion, forest fires, etc.) and the development works.
Obviously, the above represent a shift of the archaeological research towards developing new cultural strategies based on information technologies. Yet, there are two main challenges that need to be faced in the immediate future: firstly, the development of a common strategy regarding the management of antiquities, the creation of homogeneous and unified databases and the integration or modification of the existing management systems and secondly, the dissemination of information aiming towards the better exploitation and enhancement of the Cultural Geographic Information Systems (C.G.I.S.).
The Laboratory of Geophysical - Satellite Remote Sensing & Archaeo-environment applies satellite remote sensing techniques and advanced image processing methodologies for in projects dealing with the preservation, monitoring and management of the environmental resources (natural and cultural).
The Laboratory is using a number of intelligent processing software packages for manipulation of satellite imagery and GIS. Digitization tablets, scanners, workstations and GPS are also supporting the research projects. The sophisticated geophysical instrumentation can be also used in conjunction to the above techniques when needed. The lab is mostly involved in research dealing with the natural and cultural resources assessment and management.
The Laboratory conducts small and large scale geophysical surveys of archaeological sites for mapping the archaeological relics and increase the efficiency of the excavation activities. Both, geophysical prospection and satellite remote sensing contribute in the mapping of the subsurface archaelogical monuments, the management and conservation of the archaeological sites and the better exploitation of the environmental and cultural resources.
Geophysical prospection techniques and satellite remote sensing/G.I.S. are used for the preservation, monitoring and management of the environmental resources (natural and cultural). The Lab is also involved in research of the environmental consequences of technical construction works, environmental pollution and geological mapping/hydrogeology. Geographic Information Systems, classification techniques and thematic mapping is applied together with image processing techniques for the assessment and management of the natural and cultural resources (landuse, protection areas, urban planning, etc.).
The Laboratory is also conducting research on the biological remais from archaeological excavations, aiming to the reconstruction of the ancient environment.
The Laboratory of Geophysical - Satellite Remote Sensing & Archaeo-environment has performed a number of geophysical prospection surveys in Greece and abroad (Cyprus, Egypt, Hungary, a.o.), offering its services to the Greek Archaeological Service, Universities and Higher Institutions. The researchers of the Laboratory are also dealing with the training of researchers and students through hand-on experience in the field and lecture series.
The Laboratory uses the most modern and precise equipment for fieldwork and sophisticated computer facilities and software for processing and mapping of the geophysical and remote sensing data. Geophysical investigations include the use of caesium, proton and fluxgate magnetometers/gradiometers, soil resistivity and conductivity techniques, microgravity, seismic, electric tomography, ground penetrating radar (with a variety of antennas) (G.P.R.), Global Positioning Systems (G.P.S.) and magnetic susceptibility measurements. The Lab is also equipped with the necessary instruments for macro and micro analysis of archaeo-environmental remains. Digitization boards, scanners, color plotters and printers guarantee the high quality presentation of the results and maps.
In large development projects, geophysical investigations constitute a necessary tool for the assessment and management of archaeological sites. Aerial photography and satellite digital imagery are able to locate and confine areas of probable archaeological interest.
Surface surveys in conjunction to other remote sensing techniques (geophysical, aerial, satellite) can be combined through a Geographic Information System for a better geographic registration of the archaeological finds and a productive management of archaeological information.
A geophysical prospection project consists of two phases: the field work and the lab (data analysis and processing) phase. The fieldwork usually takes a period of a week for covering an area of about 5-8,000 m2, with a 1m sampling interval. Geophysical measurements are conducted in specific regions of interest, following the consultation of the supervising archaeologist.
The technical support of the Laboratory includes the mapping of large areas with a dense sampling interval, which is usually specified depending on the needs of the survey and the land cover. In this way, it is possible to locate architectural remnants, wall structures, trenches, kilns, roads, firehearths, pits and other features of archaeological interest. A much more systematic approach could even estimate the depth to the archaeological features and identify the different occupation layers of a site. Processing of the geophysical data is followed by the production of maps which represent the geophysical targets of probable archaeological nature.
The analysis and processing of the geophysical data includes the mapping of surface features, the application of mathematical filters, the drawing of the geophysical grids, image processing techniques, modelling and mapping of the geophysical anomalies, etc. The final report is in most cases ready within a period of 3-6 months after the end of the fieldwork period, depending on the availability of related information and urgency of the project. In a few cases, a first-hand processing and mapping of the data is possible on the site, providing (almost) ´´real-time´´ information on the results of the geophysical survey.
One of the most commonly used geophysical techniques in the detection of "shallow structures" is the electrical method, which is also known as "Direct Current method". The purpose of the method is the determination of the subsurface resistivity contribution, by conducting measurements at the surface of the earth.
To achieve this, electric current is inserted into the ground via two electrodes and the potential difference, which is caused by the inserted current, is measured in two other electrodes. The measured potential difference gives an image for the difficulty of the current flow through the subsurface. This is an indication of the electrical resistance of the subsurface. In figure 1 a typical array of four electrodes A, B (current electrodes) and M, N (potential electrodes) is presented.
The resistivity method is widely used in Hydrogeology to detect aquifers, in Technical Geology to find the stable rock and the cavities and in assessing the hydraulic properties of the subsurface e.t.c., for environmental purposes in detecting the ground-water pollution, in the search of geothermic areas and mines and in Archaeometry.
The resistivity depends on hydrological-hydrogeological conditions, the chemical composition of the water, the dissolved ions in it, the porosity of the formation, the possible fractures, the temperature and pressure and the topography.
As it was mentioned above resistivity depends on many factors and it doesn´t comprise a distinguishing property of specific formations, since the resistivity variability may have a large range in the same formation. Thus the interpretation of resistivity measurements must be treated with caution and must always depend on the available geologic information of the area (geologic maps, drills).
The procedure of measurements´ acquisition depends on the use of four electrodes, two in order to insert current and two to measure the potential difference. The current probes are inserted into the ground in a depth of a few centimeters and distances that vary from a few to several hundred of meters.
Due to the fact that earth is inhomogeneous and anisotropic the measured resistivity depends on the subsurface geoelectrical distribution and the geometric arrangement of the probes. In order to include these factors in the actual measurements the term apparent resistivity is used.
Resistivity Survey Methods
Soundings: The purpose of the vertical electrical resistivity sounding (VES) is to investigate the variation of the resistivity with depth. The whole procedure is based on the assumption that the subsurface has a horizontal stratigraphy. In other words it consists of discrete, horizontal, homogeneous and isotropic layers. The array that is commonly used in VES is the Schlumberger array. VES are mainly used in Hydrogeology.
The measurements are taken with gradually increasing distances of the current electrodes (the potential electrodes remain constant). As the distance between current probes is increased, there is also an increased in the depth at which the current penetrates below the surface of the ground increasing the depth of investigation. In this way, an estimate of the vertical resistivity distribution below the centre of the array is determined.
Profiles: Profiles are used to detect lateral resistivity changes. In contrast to the VES, the distances between the probes remain stable and measurements are taken by moving the whole array with constant step interval. By this way the lateral resistivity changes at a steady depth are mapped. The most widely used arrays for profiling survey are Wenner, Pole - Pole, Dipole - Dipole and Twin - Probe array.
Especially in Archaeometry the Twin - Probe (Figure 3) array is very popular because the data can be collected within a small period of time and are easily interpreted. The method also has a relative good spatial distribution. Two remote probes faraway from the survey area are used (one for the current and one for the potential), which there are placed at a distance equal 30 times of the distance between the remote probes. (e.g. 15 meters away if the distance between the mobile probes is 0.5 meters). The mobile electrodes (one for the current and one for the potential) are moved simultaneously with a constant step. The spatial resolution ability of the method is 1.0a, while the depth of investigation can be 1.0 - 2.0a, where a is the mobile probes´ separation. The accuracy of the measurements is of the order of 1 - 0.1 O.
Tomography (2-D imaging): 2-D electrical surveys are employed for gathering information for the horizontal and the vertical variation of the resistivity. These type of measurements are also used in the quantitative interpretation of buried structures (determination of depth, size, shape of the body). 2-D electrical tomography is also applicable in detecting buried antiquities.
Nowadays 2-D resistivity surveys have been developed and can be used in large scale surveys. A series of electrodes are placed at the surface of the ground and via a multiclone cable and a multiplexing system, the resistivity measurements are obtained automatically along profiles, with a gradually increasing distance between the probes.
It is quite difficult to interpret these kinds of data instantly. The data must be processed with the algorithms of non-linear 2-D inversion. It must be noted that sections of this type are carried out of specific regions of interest, because of the difficulties that have to be encountered during the conduction of the field survey.
Gravity and Magnetic Methods
Gravity and magnetic methods consist of one of the first used techniques in the detection of subsurface structures. The relatively easy procedure in data acquisition combined with the low cost in relation to other geophysical methods (seismic reflection) make them very popular methods.
As their name reports, using these methods, it is tried two potential fields to be measured. For this reason these methods are mainly known as "potential field methods". There are cases where these methods can be used simultaneously, as the transition from one field to another can be accomplished via the Poisson relation. Poisson equation connects the gravity and the magnetic potential that a body causes, provided the density and the magnetization distribution is allocated uniformly in his whole volume. Furthermore many of the applied processing techniques to the collected data are common to the both methods.
The goal of the magnetic methods is to detect the subsurface´s magnetic changes because of the presence of structures which are found under the surface of the earth. During the application of a magnetic survey the local magnetic field of the earth is measured at a distance above its surface. The height of the sensor ranges from 0.5 meter, (in the case of buried antiquities detection), to some hundred of meters above the surface´s topography of an area, for the anomalies´ detection which are related with the geology of this area.
In order to measure the magnetic field, either magnetometers which measure the total intensity of the magnetic field (proton magnetometers) or gradient magnetometers (proton or flux) which measure the vertical gradient of the magnetic field are employed. The accuracy of these instruments is of the order of 0.01 - 1 nT. In the detection of archaeological remains the measurements are taken with a steady sampling step in rectangular small dimensional grids (10x10 ? 20x20), placing the sensor to a small and steady distance from the surface of the earth.
Underground bodies which have different magnetic properties from the rest of the subsurface, change to a smaller or bigger degree the local magnetic field. The magnetic field´s deformation is observed as an "anomaly" to the measurements. These anomalies are caused by different reasons which vary according to the intensity of the magnetic field and the geometric shape of these. Ditches, places of burning, kilns, architecture structures or concentration of organic material can cause these anomalies. The magnetic anomalies depend on the direction of the earth´s magnetic field and on the direction of the magnetization vector. For this reason the magnetic anomalies are mainly dipolar.
The magnetic anomalies are directly related to the soil´s magnetic susceptibility. Regions with an increased magnetic susceptibility (related to the environment) appear as positive magnetic anomalies while regions with decreased magnetic susceptibility appear as negative anomalies. Both of these kinds of anomalies are equally interesting in the procedure of the magnetic data interpretation.
In general the existence of buried antiquities in the subsurface is usually accompanied by an increase in the magnetic susceptibility causing a weak magnetic field which alters the local magnetic field of the earth. Total field magnetometers measure the resultant of the weak local magnetic field and the stronger earth´s magnetic field. Gradient magnetometers (flux magnetometers) measure the vertical or the horizontal component of the magnetic field. These kinds of magnetometers comprise the most efficient instruments that measure the local magnetic field and its variations due to shallow depth remains.
Generally the variation of the local magnetic field because of the existence of subsurface archaeological remains is relatively small, because of the weak remanent magnetization. This variation is increased as the magnetic susceptibility of archaeological targets is increased (burning phenomena, density in iron components e.t.c.). The instruments that are required for the detection of archaeological ruins must have high accuracy, great sensitivity and being trustworthy. These instruments measure the magnetic field in an accuracy of order of 0.1 - 1 nT (0.1 - 1 x 10-9 T). Even bigger accuracy of the order of pT (0.001 - 0.01 nT) is possible using the Cesium magnetometers, but there is the danger to insert high level of outside noise.
It must be noted that the earth´s magnetic field isn´t stationary but it changes with time. The one variation that is the most interesting is the daily one. These transient variations affect the magnetic measurements and can not be predicted.
Under normal circumstances the intensity of the magnetic field varies from 50 - 100 nT. In case that a magnetic storm occurs the magnetic field is more active and the diurnal variations are of the order of 100 - 500 nT. For this reason it is a necessity to observe the change of the magnetic field while the magnetic survey is conducted, using a second magnetometer. The use of gradient magnetometers has the advantage to eliminate the drastic changes of the magnetic field and to rebate the geologic influence.
Gravity methods aim to determine the subsoil´s gravity changes conducting measurements of the gravity field on the surface of the earth. Namely gravitometry aims towards the detection of structures with different density compared to their environment (either positive or negative). These methods depend on the Newton´s gravity law. This law defines the attractive force which is exercised between two bodies with a specific mass and they are separated of a specific distance.
The modern instruments that are used to measure the gravity field are called gravitometres. Their main function principle depends on the existence of a spring. At the edge of this spring a mass is hanged. The springs which are known as "zero length springs" are commonly used nowadays to the modern gravitometers.
Gravitometers are very sensitive instruments and they are affected by temperature and pressure changes. For this reason gravitometers are placed in boxes, where temperature and pressure are maintained steady using various techniques. Furthermore the changes of the springs´ elastic properties have to be considered although many times it is difficult to predict them.
In order to measure the gravity field, it is necessary to locate a base station in the area of interest. Afterwards a net of points that comprise a grid or they are at equal spaces along a profile must be determined. All the necessary corrections (reduction to the same latitude, "free-air" reduction, Bouguer reduction, topographic reduction) must be applied to the collected data, before they will be processed and interpreted.
The advantage of these methods in relation to the magnetic methods is the fact that the anomalies are unipolar. This means that they maximize or minimize directly above the subsurface body that causes the irregular gravity field. This is ought to the fact that gravity anomalies depend only on the body´s gravity distribution. In contrast magnetic anomalies depend on the earth´s magnetic field direction and on the direction of the magnetization vector. This fact causes the magnetic anomalies to appear as dipolar.
Ground Penetrating Radar
Radar is the acronym for RAdio Detecting And Ranging. It is a system that uses the high frequency electromagnetic radiation.
The Ground Penetrating Radar method has the same operation principle with the seismic reflection method. This geophysical technique is applicable to strata mapping in the cases of soils and rocks and depends on the different electrical properties that various materials have. The development of the method started mainly in 1956, but accelerated considerably after 1970 as a result of the tremendous progress that took place in electronics and computer technology after 1960.
G.P.R. can be used in a series of applications like the mapping of the bedrock depth, the determination of the stratum thickness and the aquifer depth, the location of physical and artificial cavities in the subsurface, cracks in the bedrock and the tracing of the changes in the rocks´ composition. The method is specially used in Archaeometry for the detection of buried antiquities.
A high frequency electromagnetic radiation is transmitted in the ground and the reflected waves are recorded. The propagating electromagnetic energy in the ground depends on the subsoil´s electrical properties, the conductivity and the dielectric constant. Basically the method depends on the record of the waves reflected on surfaces that divide regions with different electrical properties.
G.P.R. is similar to the seismic reflection method. A high frequency, small duration electromagnetic pulse is transmitted into the ground. This pulse (signal) is diffused in the subsurface materials and its direction depends on its properties. A part of the pulse energy is reflected on the surface that separates materials with different properties and is recorded at a receiver on the surface. The remaining pulse energy is diffused at deeper levels.
The time between the transmitting and the receiving pulse depends on the velocity along the trace the pulse followed. This time can be measured and if the electromagnetic wave propagation velocity is known then the depth of the reflector can be determined. In most of the geologic materials the conductivity and the dielectric constant (relative permittivity) are the main parameters that affect the pulse. Furthermore the absorption of the signal depends mainly on the antenna frequency, the conductivity and the dielectric constant.
The maximum penetration depth of the G.P.R. depends on the absorption of the electromagnetic waves. The absorption increases with frequency and thus a smaller frequency is used for detecting the deeper targets. On the other hand the resolution of the method is decreased as the frequency is increased. For instance G.P.R. system working at the range of 25-50 MHz can investigate depths over 50 meters in soils with low conductivity (smaller than 1ns/m) like sand and gravels.
The Radar recordings (radiograms) are placed one beside the other so as to construct a section that simulates the real subsurface electrical section, producing information of the changes of the electrical properties with depth.
The Laboraroty of Geophysical-Satellite Remote Sensing and Archaeo-environment undertakes the analysis of biological remains form archaeological excavations, aiming to the reconstruction of aspects of the ancient environment. Such an analysis leads to a better understanding of the environmental and economic variables, which have affected human activity and behavior in the past. It also works towards the illumination of aspects of social behavior which involve the acquisition, management and consumption of food and biological raw materials.
Through the retrieval of a variety of bio-archaeological remains, and detailed identification and recording of animal remains (mammals and fish), the Lab contributes to the reconstruction of archaeological landscapes and the managements of archaeological sites. Furthermore, the investigation and study of ancient ecosystems leads to a better understanding on environmental management.
The Lab is also contributing to the better understanding of the archaeological evidence. The analysis of bio-archaeological remains sheds light to basic aspects of ancient economy (i.e. available natural resources and their management, nutrition, animal husbandry, hunting, fishing, and so forth), as well as diet and related aspects of life.
As aspects of everyday life, such as agriculture, animal husbandry, fishing and diet, fall under the influence of world-systems, research, which focuses on the interaction between humans and their environment in the past, becomes crucial. Such research not only provides examples of sustainable management of natural resources but also highlights the individuality of gegraphically specific small scale communities.
Zoo-archaeology is the study of the past interactions between humans and animals. It is based on animal bones, found during archaeological excavations. It also uses additional data, such as artefacts, documentary sources, art representations, etc.
Animal remains are very common finds in archaeological excavations and they are often accurate witnesses of everyday economic conditions and actions which have passed without leaving any other visible traces.
The zoo-archaeological research follows three main steps:
During the archaeological excavation, many animal remains are collected, including bones of mammals, fish and birds. Hand picking, dry sieving and water flotation are some of the methods employed, each leading to a more or less representative recovery.
Every animal bone found in an excavation bears some information about the animal's physiology as well as on the management of the live animals and the carcasses. Observations on the bone refer to the anatomical part it represents, the animal it belongs to, its sex and maturity, as well as the degree/method of its fragmentation, its preservation state and possible pathologies, cut marks, working evidence etc. Using a basic statistical analysis all this information elucidates such aspects of elementary human/animal interactions as :
Observations on the preservation of the bones, are used as a guide to the reconstruction of the taphonomic history* of the assemblage and often of the excavated site itself.
The basic information derived from the animal bones is combined with other sets of data, such as related architectural structures and artifacts, written sources, art representations. They are analysed in the light of ecological observations and ethnographic paradigms. The aim is to build a picture on the past interactions between animals and humans.
Interpretations of animal bone assemblages usually refer to the nature of the environment from which the animals under study originate and the methods developed by humans to manage the animals (hunting, herding, pastoralism, etc). The socio-economic implications of the above, special uses of animals (e.g. sacrifice), as well as symbolic/ideological values invested on them are also explored.
* Taphonomic history: refers to the processes which have affected the bones since the moment it seized being alive to the time of analysis. It involves factors such as crushing, trampling, digesting, and the erosion of bones through weathering.
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2. Athos Agapiou, «Γεωπληροφορική στη Διαχείριση Πολιτιστικής Κληρονομιάς», Τμήμα Πολιτικών Μηχανικών και Μηχανικών Γεωπληροφορικής, Τεχνολογικό Πανεπιστήμιο Κύπρου (in progress, 2009-)
3. Sylviane Dederix, The Minoan Funerary Landscape, Universite Catholique de Louvain (UcL) (in progress, 2009-)
4. Dimitris Alexakis, "Η Συμβολή της Γεωμορφολογίας, με την βοήθεια της Τηλεπισκόπησης και των Γεωγραφικών Συστημάτων Πληροφοριών, στη Χαρτογράφηση Αρχαιολογικών Θέσεων", Τμήμα Γεωλογίας, Τομέας Φυσικής και Περιβαλλοντικής Γεωγραφίας, Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης (2003 - 2009).
5. Sofia Topouzi, "Διερεύνηση του Οικιστικού Πλέγματος της Νήσου Ικαρίας κατά την Αρχαιότητα", Tομέας Κλασσικής Αρχαιολογίας, Τμήμα Ιστορίας & Αρχαιολογίας, Πανεπιστήμιο Αθηνών (2001 - 2008)
6. Nikos Papadopoulos, "Ανάπτυξη αλγορίθμων για την τρισδιάστατη αντιστροφή γεωηλεκτρικών δεδομένων που προέρχονται απο αρχαιολογικούς χώρους", Τμήμα Γεωλογίας, Τομέας Γεωφυσικής, Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης (2003 - 2007)
7. Emanuela de Marco, "Oλοκληρωμένες Μαγνητικές και Αρχαιομαγνητικές Μετρήσεις σε Αρχαιολογικούς Χώρους: Συμβολή στις Καμπύλες Αναφοράς για τον Ελληνικό Χώρο", Τμήμα Γεωλογίας, Τομέας Γεωφυσικής, Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης (2003 - 2006)
8. Steven Soetens, "Minoan Peak Sanctuaries: Building a Cultural Landscape Model Through a GIS Αpproach". Supervisors & Supporting Institutes: Prof. Jan Driessen - Departement d'archeologie et d'histoire de l'art, Universite Catholique de Louvain (UcL), Belgium & Dr. Apostolos Sarris - Laboratory of Geophysical-Satellite Remote Sensing & Archaeo-environment, Institute of Mediterranean Studies, Foundation for Research and Technology, Hellas (F.O.R.T.H.) (1999 - 2006).
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