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Matched filter separation of magnetic anomalies caused by scattered surface debris at archaeological sites
Author(s) -
Sheriff Steven D.
Publication year - 2010
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 - 10.3997/1873-0604.2009057
Subject(s) - geology , magnetic anomaly , wavelength , magnetic field , debris , amplitude , magnetic dipole , filter (signal processing) , intensity (physics) , magnetic separation , signal (programming language) , geophysics , optics , physics , oceanography , quantum mechanics , computer science , computer vision , programming language
Randomly scattered debris, some of it ferromagnetic, on or near the ground surface regularly degrades magnetic data acquired for archaeological purposes. These sources create short‐wavelength high‐amplitude dipolar anomalies in total field magnetic intensity maps and they can dominate maps of the vertical magnetic gradient. Thus, we generally wish to separate longer wavelength anomalies created by features of interest, such as foundations or building perimeters, from the shorter wavelength anomalies created by debris on or near the ground surface. Matched bandpass filtering, employed extensively in the aeromagnetic industry, is an effective way to separate magnetic anomalies arising from different depths. It entails fitting the radially averaged power spectrum of the total field magnetic data with a series of power spectra corresponding to simple equivalent layers at the archaeological site. We show that applying matched bandpass filtering to a set of total field magnetic intensity data yields two equivalent layers with excellent separation of near‐surface sources from deeper sources of interest. The benefit of this approach over enhancing surface features using magnetic gradiometry, analysis by upward continuation, or the analytic signal is that we isolate the source layers without losing information.