**6. Geophysical prospection techniques: From mapping to CRM**

**Figure 22.** Models for Byzantine and Post Byzantine churches of Cyprus using topometric measurements and GIS tools

Moreover, laser scanners can be used for monitoring purposes as shown by Themistocleous et al., (2012a). In order to monitor the effects of air pollution, the Limassol Castle is being documented every year with the 3D laser scanner. Areas of the castle which show deteriora‐ tion on the 3D laser scanner will have samples taken to determine the chemical analysis of the surface to establish if the deterioration was caused by air pollution or natural causes. Photographs of the castle were also taken and applied to the 3D laser scanned point cloud. A direct visual comparison between the intensity of the laser scanner and close range photo‐ graphs of the cracks in the Limassol Castle indicate that observation of intensity values can indicate the presence -or not- of possible cracks in the monument. (Figures 23 and 24). Simi‐ lar conclusions can be drawn when laser scanner intensity is compared with ultrasonic

**Figure 23.** Visual comparison of the laser intensity and close range photographs near a crack

(Agapiou et al., 2010c).

80 Remote Sensing of Environment: Integrated Approaches

measurements.

In terms of ground based remote sensing, there is a wide range of surveying techniques that are focus targeted towards the shallow or medium mapping of the subsurface antiquities or even of the deeper geological layers that may have covered the cultural strata. The various methods, in‐ cluding magnetometry, soil resistance or electromagnetic methods (EM), ground penetrating radar (GPR), and seismic, are based on the measurement of different physical quantities and the complementary application of them (the manifold approach) produces datasets that can match each other and maximize the information content of the geophysical interpretation (Sar‐ ris, 2012). Depending on the method and the configuration of the techniques, it is also possible to have different penetration depths and operation in diverse environmental settings (rural or urban) to address a various topics related to the mapping of archaeological sites and archaeoenvironment, the preservation of monuments, e.t.c. Geophysical approaches can be applied in planned excavations, rescue archaeology, archaeolandscape studies, building conservation and cultural resources management (Sarris & Jones 2000).

In general, magnetic techniques using the measurement of the total geo-magnetic field in‐ tensity or of the gradient of it or one of its components can be helpful in identifying architec‐ tural relics or residues of habitation and workshop activities. Magnetometry techniques have been successfully used to map the relics of settlements and reveal the town planning system. Mud brick foundations of Late Neolithic houses together with pits and other details were recorded around the tell of *Sceghalom-Kovácshalom* in E. Hungary. The organic material gathered in the pits was responsible for the enhancement of the magnetic susceptibility, re‐ sulting in the good registration of the pits from the measurements of the vertical magnetic gradient. Even stronger was the magnetic signature of the foundations of the fired daub foundations and walls of the farmsteads that were recorded as thermal targets, but which at the same time were not able to register to the GPR measurements due to the high conductiv‐ ity of the soils (Monahan & Sarris 2011, Sarris, 2012) (Figure 25). The same type of thermal signature is shown in the investigation of workshops and kilns belonging to different chro‐ nological periods. In other cases, such as in *Sikyon*, Peloponnese (S. Greece), the difference of the construction materials of the structural remains of the Hellenistic/Roman city in terms of the magnetic minerals they contained was responsible for providing an accurate plan of the ancient city. Due to the soil conditions and the preservation of the site, the magnetometry survey specified the street layout and the city quarters, tracing numerous monuments inside and outside the agora limits, including temples, porticoes, a basilica, street lines, houses and industrial installations (Sarris et al., 2009; Gourley et al., 2008).

cal analyses and OSL dating of cores taken from the region and the use of geophysical techniques in the study of the dynamics of the landscape evolution (Sarris et al 2012)

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83

GPR and soil resistance techniques (including ERT) also can be used in an urbanized context in contrast to the rest of the geophysical approaches (Sarris 2008; Linford 2006). Due to a high level of ambient noise from the background anthropogenic activities and the high dis‐ turbance of the upper soil layers, the particular techniques can be adapted to resolve a num‐ ber of issues in question (Sarris & Papadopoulos 2011; Papadopoulos et al., 2009). Thus, the above methodology can be used during the course of private construction activities but also for even larger civil construction works that can deal with highways, squares, pedestrian roads, etc. In a number of instances they can even be applied within historical structures and monuments to conclude on the integrity status of the monuments. The geophysical techni‐ ques can also contribute to a more generalized risk assessment model, since it can provide information for the tectonic regime and the classification of geological strata either in terms of their resistivity (ERT), velocity of propagation of acoustical waves (seismic techniques) or even the seismic amplification factor (micro-noise horizontal to vertical spectral ratio -

**Figure 25.** Left: Comparison between magnetic and GPR prospection above structural remains of the flat settlement at *Szeghalom* site in East Hungary. Even though the foundations of the daub constructions are registered clearly to the magnetic data (left top), the high conductivity of the soils has attenuated strongly the GPR electromagnetic signals masking completely the particular area (left bottom) (Sarris 2012). Right: Comparison between magnetic and GPR prospection at the corner of the Palaeochristian fortifications of *Nikopolis*, *Epirus* (Greece). The color maps represent the GPR horizontal slices of 0.1m width for depths of 0.5 (top right), 1 (bottom left) and 1.5m (bottom right) approximately. The remains of a structural complex are obvious in the magnetic data. The GPR managed to register reflectors originating from various depths, such as a curving path at the top layers and a section of decumanus maximus at the lower bottom of the surveyed area. The latter was not clearly resolved in the magnetic data as the high surface con-

centration of sherds created a uniform magnetic background masking of the area of interest.

(Figure 26).

HVSR) (Sarris et al., 2010).

Similar is the operation of the EM and soil resistance methods, which, together with the GPR, are considered ideal to resolve features related to structural remains, champers, voids and tombs. These methods are considered to be active measuring techniques. The particular methodology has been used successfully in resolving the foundations of build‐ ings, road networks, and funeral residues. Of particular interest is their ability to operate in different frequencies (EM and GPR) or configurations (soil resistance) allowing a larg‐ er or smaller penetration depth. In this way, it is possible to provide valuable informa‐ tion regarding the subsurface stratigraphy. For example, the decrease of the GPR antenna frequency can provide a larger penetration to the soil strata. In addition, the multiple re‐ flections of the GPR electromagnetic signals originating from adjacent (usually parallel) transect can create images of the subsurface layers (of various widths) by increasing depth (depth slices) (Figure 25). In a similar way, vertical electric soundings measure re‐ sistivity variations with depth by increasing gradually current electrode separation while the center of the electrode configuration, remains stationary. Based on the same princi‐ ple, the electrical resistivity tomography provides information for both the lateral and vertical variations in the resistivity of the soil and, based on 2D or 3D inversion algo‐ rithms; it can produce a 3D reconstruction model of the subsurface (Papadopoulos et al., 2011, Sarris 2008).

The use of the EM, electrical resistivity tomography (ERT) and seismic techniques is more appropriate for the deeper mapping and their employment is usually applied in ar‐ chaeolandscape studies. This was the case of *Priniatikos Pyrgos*, where the integrated ap‐ plication of ERT and seismic tomography techniques processed by 3D inversion algorithms were capable to contribute to the archaeoenvironmental reconstruction of the *Priniatikos Pyrgos* at Istron, E. Crete, providing indications regarding the ancient harbor of the nearby settlement (Shahrukh et al 2012). The particular methods were the only sol‐ ution to provide information about the deposits that exist in the coastal area of *Priniati‐ kos Pyrgos*: carstic formations of medium to high permeability and alluvium deposits of variable permeability, probably originating by past landslide episodes and periodic flood‐ ing of the Istron River, have covered the ancient harbour at depths varying from 20-40m below the current surface. Similarly, electromagnetic and soil resistance measurements re‐ vealed the movement of the older Istron River branches, which appeared to be directed to the sea from both sides of the settlement, leaving probably a small path to the main‐ land from the SW direction. The above results were also supported by the sedimentologi‐ cal analyses and OSL dating of cores taken from the region and the use of geophysical techniques in the study of the dynamics of the landscape evolution (Sarris et al 2012) (Figure 26).

ity of the soils (Monahan & Sarris 2011, Sarris, 2012) (Figure 25). The same type of thermal signature is shown in the investigation of workshops and kilns belonging to different chro‐ nological periods. In other cases, such as in *Sikyon*, Peloponnese (S. Greece), the difference of the construction materials of the structural remains of the Hellenistic/Roman city in terms of the magnetic minerals they contained was responsible for providing an accurate plan of the ancient city. Due to the soil conditions and the preservation of the site, the magnetometry survey specified the street layout and the city quarters, tracing numerous monuments inside and outside the agora limits, including temples, porticoes, a basilica, street lines, houses and

Similar is the operation of the EM and soil resistance methods, which, together with the GPR, are considered ideal to resolve features related to structural remains, champers, voids and tombs. These methods are considered to be active measuring techniques. The particular methodology has been used successfully in resolving the foundations of build‐ ings, road networks, and funeral residues. Of particular interest is their ability to operate in different frequencies (EM and GPR) or configurations (soil resistance) allowing a larg‐ er or smaller penetration depth. In this way, it is possible to provide valuable informa‐ tion regarding the subsurface stratigraphy. For example, the decrease of the GPR antenna frequency can provide a larger penetration to the soil strata. In addition, the multiple re‐ flections of the GPR electromagnetic signals originating from adjacent (usually parallel) transect can create images of the subsurface layers (of various widths) by increasing depth (depth slices) (Figure 25). In a similar way, vertical electric soundings measure re‐ sistivity variations with depth by increasing gradually current electrode separation while the center of the electrode configuration, remains stationary. Based on the same princi‐ ple, the electrical resistivity tomography provides information for both the lateral and vertical variations in the resistivity of the soil and, based on 2D or 3D inversion algo‐ rithms; it can produce a 3D reconstruction model of the subsurface (Papadopoulos et al.,

The use of the EM, electrical resistivity tomography (ERT) and seismic techniques is more appropriate for the deeper mapping and their employment is usually applied in ar‐ chaeolandscape studies. This was the case of *Priniatikos Pyrgos*, where the integrated ap‐ plication of ERT and seismic tomography techniques processed by 3D inversion algorithms were capable to contribute to the archaeoenvironmental reconstruction of the *Priniatikos Pyrgos* at Istron, E. Crete, providing indications regarding the ancient harbor of the nearby settlement (Shahrukh et al 2012). The particular methods were the only sol‐ ution to provide information about the deposits that exist in the coastal area of *Priniati‐ kos Pyrgos*: carstic formations of medium to high permeability and alluvium deposits of variable permeability, probably originating by past landslide episodes and periodic flood‐ ing of the Istron River, have covered the ancient harbour at depths varying from 20-40m below the current surface. Similarly, electromagnetic and soil resistance measurements re‐ vealed the movement of the older Istron River branches, which appeared to be directed to the sea from both sides of the settlement, leaving probably a small path to the main‐ land from the SW direction. The above results were also supported by the sedimentologi‐

industrial installations (Sarris et al., 2009; Gourley et al., 2008).

82 Remote Sensing of Environment: Integrated Approaches

2011, Sarris 2008).

GPR and soil resistance techniques (including ERT) also can be used in an urbanized context in contrast to the rest of the geophysical approaches (Sarris 2008; Linford 2006). Due to a high level of ambient noise from the background anthropogenic activities and the high dis‐ turbance of the upper soil layers, the particular techniques can be adapted to resolve a num‐ ber of issues in question (Sarris & Papadopoulos 2011; Papadopoulos et al., 2009). Thus, the above methodology can be used during the course of private construction activities but also for even larger civil construction works that can deal with highways, squares, pedestrian roads, etc. In a number of instances they can even be applied within historical structures and monuments to conclude on the integrity status of the monuments. The geophysical techni‐ ques can also contribute to a more generalized risk assessment model, since it can provide information for the tectonic regime and the classification of geological strata either in terms of their resistivity (ERT), velocity of propagation of acoustical waves (seismic techniques) or even the seismic amplification factor (micro-noise horizontal to vertical spectral ratio - HVSR) (Sarris et al., 2010).

**Figure 25.** Left: Comparison between magnetic and GPR prospection above structural remains of the flat settlement at *Szeghalom* site in East Hungary. Even though the foundations of the daub constructions are registered clearly to the magnetic data (left top), the high conductivity of the soils has attenuated strongly the GPR electromagnetic signals masking completely the particular area (left bottom) (Sarris 2012). Right: Comparison between magnetic and GPR prospection at the corner of the Palaeochristian fortifications of *Nikopolis*, *Epirus* (Greece). The color maps represent the GPR horizontal slices of 0.1m width for depths of 0.5 (top right), 1 (bottom left) and 1.5m (bottom right) approximately. The remains of a structural complex are obvious in the magnetic data. The GPR managed to register reflectors originating from various depths, such as a curving path at the top layers and a section of decumanus maximus at the lower bottom of the surveyed area. The latter was not clearly resolved in the magnetic data as the high surface concentration of sherds created a uniform magnetic background masking of the area of interest.

**Figure 26.** Left: A 2-D view of the bedrock depth in the area of the harbour of *Priniatikos Pyrgos* resulting from the seismic refraction survey. The bluish colors indicate the deeper level of the bedrock and the dashed lines indicate the proposed location of the depression of the ancient harbour. Right: The soil resistance survey to the south of the promontory of *Priniatikos Pyrgos* indicated a 5m wide high resistance linear anomaly that extends in a SW-NE direction and is probably related to one of the older branches of the Istron River running towards the east side of the promontory. (Sarris et al 2012)

Although current trends have emphasized the fast reconnaissance of the archaeological sites through multi-sensor, multi-electrode or multi-antenna systems, the manifold ap‐ proach, which is the amalgamation of multiple geophysical techniques, as well as the fu‐ sion of the geophysical data with other types of remote sensing techniques, such as satellite imagery, LIDAR or laser scanning and orthophotos aiming towards a better and more holistic visualization of the area and a better reconstruction of the underground monuments will continue to be of crucial importance in the geophysical prospection of ar‐ chaeological context (Sarris 2012).

**Figure 27.** Right- ground control mechanism and aerial platform. Left-Low altitude airborne system including air balloon, spectro-radiometer, and researcher wearing ground control mechanism with harness (Themistocleous et al.,

Remote Sensing for Archaeological Applications: Management, Documentation and Monitoring

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85

A helium-filled balloon with a 3 m. diameter was used which was able to be raised to a height up to 200 m with a payload of up to 6kg. The Spectra Vista GER 1500 spectroradi‐ ometer was attached to the aerial platform and operated remotely. The balloon was raised to varying heights and spectroradiometric measurements were taken of the same target at different elevations. Concurrent to the spectroradiometric measurements, aerial photographs were taken using two digital cameras, one with infrared filter. The integra‐ tion of the various techniques was used in order to detect subsurface archaeological re‐ mains by examining ground anomalies identified through spectral signatures. Previous campaigns in Cyprus found that field spectroscopy can support the detection of archaeo‐ logical crop marks based on the retrieved spectral signatures over agricultural areas which are characterized as archeological areas (see Agapiou and Hadjimitsis 2011). Possi‐ ble identification of subsurface archaeological remains is based on spectral signatures anomalies. Such anomalies are observed in crops when the vegetation is under stress due to subsurface relics. Therefore, spectral signatures anomalies are expected in the red and

The low altitude airborne imaging system was tested at the Agricultural Research Institute in Paphos, Cyprus, where a simulated archaeological test field was constructed. Spectrora‐ diometric measurements and photographs in the visible and infrared range were taken over

2012b)

VNIR part of the spectrum.

### **7. Low altitude systems for supporting archaeological investigations**

Further to satellite and ground investigations, research has indicated the need for a low alti‐ tude airborne imaging systems in order to support archaeological research. This is due to the fact that such systems of low cost, with a stable platform for imaging sensors and have the ability to lift a payload equivalent to sensor equipment (Patterson & Brescia, 2008; Voer‐ hoeven, 2009; Kemper, 2012; Nebiker et al., 2008; Bento, 2008; Georgopoulos, 1982; Hailey, 2005). In this study, several technologies were merged to create an innovative low altitude airborne system supporting remote sensing and photogrammetric applications, which in‐ cludes the ability to conduct spectroscopy and aerial photography using a helium filled bal‐ loon. The complete low altitude airborne system is shown in Figure 27.

**Figure 26.** Left: A 2-D view of the bedrock depth in the area of the harbour of *Priniatikos Pyrgos* resulting from the seismic refraction survey. The bluish colors indicate the deeper level of the bedrock and the dashed lines indicate the proposed location of the depression of the ancient harbour. Right: The soil resistance survey to the south of the promontory of *Priniatikos Pyrgos* indicated a 5m wide high resistance linear anomaly that extends in a SW-NE direction and is probably related to one of the older branches of the Istron River running towards the east side of the promontory.

Although current trends have emphasized the fast reconnaissance of the archaeological sites through multi-sensor, multi-electrode or multi-antenna systems, the manifold ap‐ proach, which is the amalgamation of multiple geophysical techniques, as well as the fu‐ sion of the geophysical data with other types of remote sensing techniques, such as satellite imagery, LIDAR or laser scanning and orthophotos aiming towards a better and more holistic visualization of the area and a better reconstruction of the underground monuments will continue to be of crucial importance in the geophysical prospection of ar‐

**7. Low altitude systems for supporting archaeological investigations**

loon. The complete low altitude airborne system is shown in Figure 27.

Further to satellite and ground investigations, research has indicated the need for a low alti‐ tude airborne imaging systems in order to support archaeological research. This is due to the fact that such systems of low cost, with a stable platform for imaging sensors and have the ability to lift a payload equivalent to sensor equipment (Patterson & Brescia, 2008; Voer‐ hoeven, 2009; Kemper, 2012; Nebiker et al., 2008; Bento, 2008; Georgopoulos, 1982; Hailey, 2005). In this study, several technologies were merged to create an innovative low altitude airborne system supporting remote sensing and photogrammetric applications, which in‐ cludes the ability to conduct spectroscopy and aerial photography using a helium filled bal‐

(Sarris et al 2012)

chaeological context (Sarris 2012).

84 Remote Sensing of Environment: Integrated Approaches

**Figure 27.** Right- ground control mechanism and aerial platform. Left-Low altitude airborne system including air balloon, spectro-radiometer, and researcher wearing ground control mechanism with harness (Themistocleous et al., 2012b)

A helium-filled balloon with a 3 m. diameter was used which was able to be raised to a height up to 200 m with a payload of up to 6kg. The Spectra Vista GER 1500 spectroradi‐ ometer was attached to the aerial platform and operated remotely. The balloon was raised to varying heights and spectroradiometric measurements were taken of the same target at different elevations. Concurrent to the spectroradiometric measurements, aerial photographs were taken using two digital cameras, one with infrared filter. The integra‐ tion of the various techniques was used in order to detect subsurface archaeological re‐ mains by examining ground anomalies identified through spectral signatures. Previous campaigns in Cyprus found that field spectroscopy can support the detection of archaeo‐ logical crop marks based on the retrieved spectral signatures over agricultural areas which are characterized as archeological areas (see Agapiou and Hadjimitsis 2011). Possi‐ ble identification of subsurface archaeological remains is based on spectral signatures anomalies. Such anomalies are observed in crops when the vegetation is under stress due to subsurface relics. Therefore, spectral signatures anomalies are expected in the red and VNIR part of the spectrum.

The low altitude airborne imaging system was tested at the Agricultural Research Institute in Paphos, Cyprus, where a simulated archaeological test field was constructed. Spectrora‐ diometric measurements and photographs in the visible and infrared range were taken over the target area. Preliminary results found that there were no significant differences in the spectral signatures in the visible range, while there was a significant difference among the spectral signatures in the NIR range as the balloon was moving up-wards (Figure 28). The study found that the spectral signature of the target can changed as a function of altitude, with higher reflectance indicated as the elevation increased.

**Acknowledgements**

**Author details**

prus

Greece

**References**

Diofantos G. Hadjimitsis1

Dimitrios D. Alexakis1

The authors would like to express their appreciation to Cyprus Research Promotion Foun‐ dation (www.research.org.cy), the European Regional Development Fund (Research Project AEIFORIA/KOINAF/0311(BIE)/O6: Managing cultural heritage sites through space and ground technologies using Geographical Information Systems: A pilot application at the ar‐ chaeological sites of Paphos), and the Greek Operational Programme "Competitiveness and Entrepreneurship" (OPCE ΙΙ) (Project Politeia) and "Education and Life Long Learning" (Ac‐ tion ARISTEIA: Project IGEAN) co-funded by the European Social Fund (ESF) and Greek National Resources. Thanks are also given to the Department of Antiquities of Cyprus for their permission to carry out field measurements at different archaeological sites of Cyprus.

Remote Sensing for Archaeological Applications: Management, Documentation and Monitoring

1 Cyprus University of Technology, Faculty of Engineering and Technology, Department of Civil Engineering and Geomatics, Remote Sensing and Geo-Environment Laboratory, Cy‐

2 Laboratory of Geophysical, Satellite Remote Sensing and Archaeoenvironment, Institute for Mediterranean Studies, Foundation for Research and Technology, Hellas (F.O.R.T.H.),

[1] Agapiou, A, Hadjimitsis, D. G, Alexakis, D, & Sarris, A. (2012a). Observatory valida‐ tion of Neolithic tells ("Magoules") in the Thessalian plain, central Greece, using hy‐ perspectral spectro-radiometric data, *Journal of Archaeological Science*, doi.org/10.1016/

[2] Agapiou, A, Hadjimitsis, D. G, Alexakis, D, & Papadavid, G. (2012b). Examining the phenological cycle of barley (hordeum vulgare) using satellite and in situ spectrora‐ diometer measurements for the detection of buried archaeological remains, *GIScience*

[3] Agapiou, A, Hadjimitsis, D. G, Sarris, A, Georgopoulos, A, & Alexakis, D. D. (2012c). Linear Spectral Unmixing for the detection of Neolithic Settlements in the Thessalian

[4] Agapiou, A, Hadjimitsis, D. G, Papoutsa, C, Alexakis, D. D, & Papadavid, G. (2011). The importance of accounting for atmospheric effects in the application of NDVI and

Plain, *Proceedings of the 32nd EARSeL Symposium*, Mykonos, Greece, May 2012.

, Kyriacos Themistocleous1

,

http://dx.doi.org/10.5772/39306

87

, Athos Agapiou1

and Apostolos Sarris2

j.jas.2012.01.001., 39(5), 1499-1512.

*& Remote Sensing* 49 (6), 854-872.

**Figure 28.** Right-Spectral signatures of vegetation at 5, 10 and 20 meters. Left-spectral differences between healthy and stressed vegetation (Themistocleous et al., 2012b)

### **8. Conclusions**

Remote sensing can contribute in several ways to archaeological research. This chapter presents some results from different cases studies in Cyprus, Greece and Hungary using several techniques of remote sensing, including satellite images, archive aerial images, geo‐ physical surveys, 3D terrestrial laser scanners, ground spectroscopy, atmospheric pollution, WebGIS and GIS analysis for monitoring purposes.

The results have shown the potential use of satellite remote sensing and ground spectrosco‐ py for the identification of buried archaeological remains through crop marks. Moreover, monitoring archaeological sites and risk assessment can be performed for several threats in‐ cluding urban expansion and air pollution. As demonstrated in this chapter, a dramatic land use change has taken place in several archaeological sites during the last decades. Such in‐ vestigations are very important for studying archaeolandscapes since can provide valuable for information for areas that are nowadays vanished. Furthermore, the potential use of ground geophysical surveys for the detection of subsurface remains was also demonstrated through several applications in Greece and Hungary, was also demonstrated. Documenta‐ tion, mapping. 3D modelling and WebGIS applications for archaeological sites and monu‐ ments are also demonstrated in this chapter.
