You Ain’t Seen Nothing Yet - Geophysical Surveying Methods as a Tool for Cultural Heritage...

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ArchaeoLandscapes Europe

Roman-Germanic Commission of the German Archaeological Institute

You Ain’t Seen Nothing YetGeophysical Surveying Methods as

a Tool for Cultural Heritage Protection

World Universities Congress

Çanakkale, 23 October 2010

Dr. Axel G. PosluschnyRoman-Germanic Commissionof the German Archaeological InstitutePalmengartenstr. 10-12D-60325 [email protected]

2 www.archaeolandscapes.eu



Content

• Introduction• Problems of invisible features in Cultural Heritage

Management• Traditional field walking• What is geophysical surveying?• Making the invisible visible • Other methods of modern surveying• Resume




Worldwide research projects of the German Archaeological Institute (DAI)




Features in Cultural Heritage Management

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Invisible Features in Cultural Heritage Management




Invisible features in Cultural Heritage Management

Braasch/Christlein1982




Traditional fieldwalking

Germania 71, 1993Ber. RGK 72, 1993




Geophysics and excavation

Ber. RGK 72, 1993




What is geophysical surveying?

• Geophysical surveying methods comprise a variety of different techniques:– Magnetometer survey– Earth resistance survey (geoelectric survey)– Ground-penetrating radar (GPR)

• They are:– non-destructive– machine-based– in most cases less expensive than excavations– can cover much larger areas than field walking, trial

trenching or even large scale excavations• Their disadvantage is the expert knowledge one has to have in

many cases to be able to handle the data derived from various measurements




What is magnetometric surveying?

• Is used to rapidly generate data of large scale areas, showing a wide variety of anomalies that have been cause by different kinds of human activities

• It uses one or more sensors to measure the gradient of the magnetic field i.e. the difference between the natural magnetic field of the Earth and the structures that have been cause by human impact

• Every kind of material has its own magnetic property, they all result in a different disturbance of the Earth’s magnetic field

• Other than earth resistance surveys, magnetometers do not usually detect walls or other stone structures (if not burned) directly

D. Peters

English Heritage 2008




Examples of magnetometric surveys

Batora et al. in press




What is earth resistance surveying?

• Earth resistance survey (geoelectric survey) is measuring the local electrical resistance by inserting two or more sensors into the ground, which produce electrical circuits

• Features like ditches often contain more moisture than the surrounding soil and therefore have less resistivity while wall structures, foundings and so on usually have a higher resistivity

• The main disadvantage of a resistance survey is the limitation caused by the need for the sensors to make direct electrical contact by the insertion of electrodes. As a result resistance survey is mainly used for smaller areas






What is ground-penetrating radar (GPR)?

• Ground-penetrating radar (GPR) is often used because of its abilities to measure not only planar features but also to estimate the depth of features. A radar signal or electromagnetic impulse is send into the ground, which causes different kinds of reflections (travel time of signals), depending on the depth and the structure of the soil and of buried features

• The resulting data represents a profile information, that can also be interpolated into a planview map by taking into account the results of several, densely measured profiles

• The main disadvantage of GPR is its dependency on ideal soil conditions. Another problem is the low speed of measurements, especially when used for larger areas


Kvamme et al. 2006




Other methods of surveying

soil marks

crop marks

Braasch 2010Landesamt 1997





• Satellite images• increasing resolution• large scale availability

Cowley et al. 2010





• LiDAR => Light Detection And Ranging = Airborne Laserscan (ALS)

• A high-resolution digital surface model (DSM) can be derived and also a „vegetation-free“ digital elevation model (DEM)

• Many national cartography agencies produce these scans which can also be used for archaeological purposes





Resume

• One can only protect what he knows - so large scale surveying to discover hidden subsoil archaeological features is not only a technique for archaeological research but also for Cultural Heritage Management

• The large variety of geophysical and other modern surveying methods have the great advantage of being non-destructive, they can amend each other and they deliver a very precise and nearly complete picture of what is hidden to the human eye

• Data from geophysical surveys are an ideal basis for decision making in urban land-use planning, it can be used to assess the threads from erosion, looting and plundering or from ploughing and it can be used for monitoring archaeological sites

• During building and construction planning the areas of archaeological interest can be taken into account, building sites can be replaced or at least the amount of pre-building research activities to excavate archaeological features can much better be assessed. So not only archaeology or Cultural Heritage Management benefits from a large scale geophysical survey but also investors and stakeholders from construction companies




Resume

• The ideal way of dealing with surveying is of course a combination of several techniques: Geomagnetic surveying to detect ditch and pit structures, geoelectrical survey to find wall structures and ground penetrating radar to know more about the depth of the hidden features - and maybe also some field walking or trial trenching to know more about the dating and the condition of the features

• Speaking about the role and the responsibilities of universities in future, I think that it should be their aim to provide expert knowledge and to teach students modern surveying methods - not necessarily enabling them to conduct these investigations themselves but to be able at least to work with data derived from such techniques and to be able to critically interpret these data and to be able to judge the interpretations of others




References

Bátora, J., Eitel, B., Hecht, S., Koch, A., Rassmann, K., Schukraft, G. and Winkelmann, K., in press. Fidvár bei Vráble (Kr. Vráble, Südwestslowakei). Untersuchungen auf einem äneolithisch-frühbronzezeitlichen Siedlungshügel. Germania (Zabern Verlag, Mainz).

Bofinger, J., 2007. Flugzeug, Laser, Sonde, Spaten – Fernerkundung und archäologische Feldforschung am Beispiel der frühkeltischen Fürstensitze / Aircraft, Laser, Sensor, Spade – Remote Sensing and Archaeological Fieldwork Using the Example of Early Celtic Princely Seats (Esslingen)

Cowley, D. C., Standring, R. A., Abicht, M. J. (eds.), 2010. Landscapes through the Lens. Aerial Photographs and Historic Environment. Occasional Publication of the Aerial Archaeology Research Group No. 2 (Oxford, Oakville)

English Heritage 2008. http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf

English Heritage 2010. http://www.english-heritage.org.uk/publications/light-fantastic/light-fantastic.pdf

Kvamme, K., Ernenwein, E., Hargrave, M., Sever, Th., Harmon, D., Limp, F., Howell, B., Koons, M. and Tullis, J., 2006. New Approaches to the Use and Integration of Multi-Sensor Remote Sensing for Historic Resource Identification and Evaluation. SERDP Project SI-1263 (Fayetteville). http://www.serdp.org/Research/ upload/SI-1263-FR.pdf

Landesamt für Denkmalpflege Hessen (ed.), 1997. Zeitspuren. Luftbildarchäologie in Hessen (Wiesbaden)




Thank you very muchfor your attention

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You Ain’t Seen Nothing Yet - Geophysical Surveying Methods as a Tool for Cultural Heritage...

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