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Geoelectrical Surveying of Archaeological Sites

Published online by Cambridge University Press:  27 May 2014

L. S. Palmer
Affiliation:
Honorary Curator, Wells Museum, Somerset

Extract

Archaeologists have for some time been employing geoelectric resistivity methods to locate buried remains in order to avoid wasteful trial-and-error excavations. The results have been successful in some cases, but unexpectedly disappointing in others. The purpose of this paper is to indicate some of the peculiar difficulties which arise when applying the usual techniques suitable for deep surveys to the location of resistance anomalies buried at relatively shallow depths below the surface. The difficulties which have been experienced depend mainly on the fact that, for small electrical resistance discontinuities at shallow depths, factors arise which are negligible with deep surveys. In other words, when the dimensions and depth of an anomaly (such as a cist in a Bronze-age tumulus or the buried foundations of a Roman Wall) are comparable with the distance between the electrodes, then the usual theoretical assumptions underlying deep surveys need to be re-examined.

Type
Research Article
Copyright
Copyright © The Prehistoric Society 1960

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References

page 65 note 1 Wenner, F., ‘Method of measuring Earth Resistivity’, Bull. U.S. Bureau of Standards, vol. 12, p. 469, 1916CrossRefGoogle Scholar.

page 65 note 2 Palmer, L. S., ‘Examples of Geoelectric Surveys’, Proc. Inst. Elect. Engs., vol. 106 A, pp. 231–44, 1959Google Scholar.

page 66 note 1 An area survey entails a series of resistivity measurements at a number of points or stations distributed over a given area. With a linear survey the stations are sited along a given line.

page 66 note 2 Professor R. J. C. Atkinson has kindly pointed out that, by using a grid of equilateral triangles, there will be a larger number of stations per unit area without any decrease in their distance apart.

page 66 note 3 ‘Isograph’ is a more convenient term but less satisfactory from an etymological point of view. The word ‘Contour’ is incorrect and misleading.

page 69 note 1 From further theoretical considerations it can be shown that for a pipe-line, wall, etc. buried to a depth of h feet below the surface, end-on traverses will cease to show double-peaked graphs when a is less than h/ or 0·71 h. When this occurs the double peaks merge into one. Unfortunately, this condition is of little practical value because the consequent limited spread of the current electrodes, namely 2a, would generally not be sufficiently large to detect small anomalies at the given depth h.