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Ploughed Soil test

Whilst resistivity results vary largely according to ground moisture, magnetometry is more influenced by geology and field conditions such as ferrous interference, trees and the surface to be walked over.

To test the influence of ploughing on magnetometry we surveyed approximately the same area twice, once when it was under stubble and again when it was ploughed.

The ploughing was deeper around the top edge of the survey area.

magnetometry and ploughing

Magnetometry survey on unploughed and ploughed field

The result appears to be that the larger anomalies can still be detected but the smaller ones (B) break up. We also appear to have gained a linear positive anomaly (A-A) which could have been mistaken for a small ditch.

The good thing here is that it shows that area magnetometer surveys will give essentially the same results each time an area is surveyed. Magnetometer scanning used to be used before automatic data logging was common but two operators could produce different results from the same area.

As to whether it is worth the risk of breaking ones ankle by surveying uneven ground is another matter.