Geomagnetometry for Archaeology

Abstract

In past decades, magnetic surveying had become popular as one of the\ud most effective techniques supporting archaeological prospecting. This is possible\ud because the existence of susceptibility contrasts between the cover soil and several\ud buried finds often causes detectable anomalies. More recently, great advances were\ud made in signal enhancement and boundary analysis of potential field anomalies,\ud thanks to methods allowing a suitable differentiation of the field without making\ud the process unstable. New three-dimensional (3D) imaging techniques provided an\ud estimate of the magnetization distribution within the subsoil by means of highresolution\ud images of the source distribution. Most of these methods are fast and\ud reliable in the presence of shallow and compact sources, just as in the case of\ud the sources usually occurring in archaeological prospecting. Nevertheless, great\ud effort was spent by the scientific community to overcome serious problems causing\ud low signal-to-noise ratio in the measurements. This chapter provides a step-bystep\ud description of technical solutions adopted to improve the quality of data and\ud to perform a better interpretation of the magnetic anomalies usually associated to\ud the presence of archaeological finds. To this end, a summary of case histories is\ud illustrated giving a general framework of the latest progress in archaeo-magnetism

New historical data on the Teutonic Order crusades in Prussia: geophysical and archaeological research into an earth‐and‐timber stronghold and city of the 1230s at Starogród, northern‐central Poland

“…In this situation, we decided to use magnetic measurements at the general recognition stage. We worked in accordance with the methodology proposed for this type of activities (Fedi, Cella, Florio, La Manna, & Paoletti, ) by performing one‐directional parallel profiling at a resolution of 0.5 m × 0.125 m for recording values of the total magnetic field vector and 1 m × 0.125 m for the calculated gradients of its components. Having the ability to locate measuring points using the global positioning system real‐time kinematic (GPS RTK) system, we obtained additional data on changes in the height of the terrain surface recorded in the device's memory.…”

Searching for the History of the Ancient Basilicata: Archaeogeophysics Applied to the Roman Site of Forentum

“…The MAG allows for the recording of a signal that is independent of the fluctuations caused by daytime variations in the Earth's magnetic field, enhancing the contrast between anomalous bodies with potential archaeological interest and the subsoil in which the objects are located. This acquisition mode provides two distinct functions of signal in the space-time domain, enabling the enhancement of results caused by the presence of anomalous bodies in the subsoil that have potentially been created by archaeological remains [17,18].…”

Towards an Operational Use of Geophysics for Archaeology in Henan (China): Methodological Approach and Results in Kaifeng

“…GPR is a non-invasive geophysical method used to detect and characterize subsurface targets by analyzing changes in the electro-magnetic (EM) properties of the medium, including the target and its surrounding [4]. In particular, GPR radiates short EM pulses into the ground and detects reflected signals generated in presence of a dielectric contrast between potential targets and surrounding soil.…”

“…The result is an average of all background noise which has been subtracted from the data; (4) energy decay based on a mean amplitude decay curve determined from all existing traces; (5) declipping to reduce too high amplitudes values; (6) a bandpass frequency filter to reduce the increase of noise affecting the radargram caused by the gain function previously adopted; (7) Kirchhoff 2D-velocity migration with a velocity estimated quantitatively using the diffraction hyperbolas generated by potential archaeological features [4,25].…”

“…Despite the increased reliability of geophysics in archaeology, the results are not always up to archaeologists' expectations As known, the capability in detecting archaeological targets, including walls, cavities, burials, depends on the physical characteristics of the targets and their matrix. Lower is the difference of physical characteristics between targets and matrix, lower is the probability in discriminating them by using any geophysical prospecting technique, including Geomagnetometry [3], Electrical resistivity tomography (ERT), Ground Penetrating Radar (GPR) [4]. This is the case of Henan and Shaanxi, where flood alluvial deposits conserve at very high depths most of the Chinese ancient cultural heritage, including buried capital cities in Luoyang, Kaifeng, and Chang'An (the current Xi'An), mainly built with rammed earth whose identification is all but easy.…”