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A multi-parameter approach for recognition of anthropogenic noise in aeromagnetic data

A multi-parameter approach for recognition of anthropogenic noise in aeromagnetic data collected over populated areas: Erzgebirge, Germany


Aeromagnetic data are routinely acquired by mineral exploration programmes. The objective is to obtain a raster image of the spatial variations of magnetic field intensity; these variations are associated with mineralogical variations in the subsurface. When the survey is conducted in a populated area, much of the signal, however, may be associated with anthropogenic sources such as buildings and roads. Identification and minimization of the anthropogenic-related signal then are essential to derive a useful product for geological mapping. In this work, we examine a scalar magnetic dataset from Geyer, Saxony, and we apply five approaches for locating regions of anomalous anthropogenic signal: signal amplitude, absolute fourth difference, signal standard deviation, enhanced horizontal gradient and curvedness. All are shown to produce similar responses, and the summation of the five results compares favourably with the standard Keating kimberlite (circular anomaly) approach for detecting anthropogenic signals. Complications arise when geological features produce signals of similar amplitude to anthropogenic sources. Differentiating the probable origin of any specific pattern can be assessed by using a 2D shape index and increased flight height. Verification of an anthropogenic anomaly is achieved by comparison of anomalous solution grids with Geographic Information System-based reference data.


Figure 1. (a) 3D image of the synthetic model of anthropogenic magnetic sources including houses (purple), warehouses (brown), industrial building (turquoise), swimming pool (green), signal tower (yellow), and sheds (blue). Individual buildings are assigned susceptibility values. Models approximate building geometry. Parallel lines show model flight line path. (b) Total magnetic intensity derived from survey along 40 m line spacing and 40 m elevation survey. (c) Amplitude of analytical signal showing large response associated with more magnetic features. Individual anomalies (the tower) produce circular anomalies. When more than one source is present, the summation of anomalies results in more complex geometry. (d) Total horizontal gradient of magnetic anomaly shows that strong magnetic gradient associated with ‘edges’ of anthropogenic sources. (e) Vertical gradient of magnetic field showing that vertical gradient peak identifies broad location of most sources. It does not detect isolated low amplitude sources


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