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The role of electromagnetic induction in development planning: the case of the Grands Philambins enigma
Author(s) -
Muller Frank,
Dabas Michel
Publication year - 2021
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.1002/nsg.12159
Subject(s) - geology , terrain , marl , geophysical survey , antenna (radio) , documentation , electromagnetic induction , mining engineering , geophysics , plan (archaeology) , seismology , paleontology , cartography , geography , computer science , engineering , structural basin , electrical engineering , electromagnetic coil , programming language , telecommunications
Spatial planning aims at constantly improving the distribution of people and activities within available space, especially near cities on ancient agricultural or industrial areas. However, a proper schedule of the development work necessitates the assessment, as precisely as possible, of the difficulties that would be encountered in terms of geotechnical abilities of the terrain and hazards resulting from previous use. In the Grands Philambins site, three different geophysical techniques were combined: multi‐depth resistivity; magnetic gradiometry; and electromagnetic induction. The aim of this study was to map, in a few days and with high measurement densities, all the electromagnetic properties of the terrain and to evidence metallic features. The acquired data were compared with prior documentation, mainly the aerial photos acquired since the middle of the 20th century. The terrain structure is complex, at the junction of geological formations composed of limestones and marls in different proportions, which were characterized by the geophysical survey. It also exhibits metallic features, among which an enigmatic 70 m diameter radially striped disc object, which was identified as non‐ferrous and corresponding to an ancient antenna earthed socket. This case study illustrates the relevance of the use of electromagnetic induction measurements in land planning studies as this method can map three independent underground properties and identify metallic features.