Figure 6-14. Magnetic Surveying
Magnetic surveying with a cesium vapor gradiometer (Geometrics, 2016) integrated with a global positioning system receiver (Trimble, 2016).
Magnetometry is a passive remote sensing method that records the magnitude of the Earth’s local magnetic field. Its sensors, called magnetometers, may be placed on the ground surface, in the air, in satellites, or in boreholes beneath the surface of the Earth. For measurements in agricultural fields, magnetometers are typically positioned within a couple of meters of the ground surface. Gradiometers, which are better adapted to emphasize magnetic field anomalies from shallow sources, are set up with two magnetometers mounted a short distance (< 1 m) apart. This arrangement allows the magnetic field gradient between them to be measured (fig. 6-14). Gradiometers have the added advantage of eliminating the need to make corrections for diurnal fluctuations in the magnetic field. Magnetic surveys using gradiometers have successfully found disturbances (e.g., backfilled trenches and excavated areas) in iron-rich soils (Rogers et al., 2005). This suggests the potential use of this technology to identify the extent and location of some anthropogenic soils, particularly in order 1 soil survey applications.
Soil Survey Manual, Ag. Handbook 18, 2017, (p. 377).
Figure 6-14. Magnetic Surveying
Magnetic surveying with a cesium vapor gradiometer (Geometrics, 2016) integrated with a global positioning system receiver (Trimble, 2016).
Magnetometry is a passive remote sensing method that records the magnitude of the Earth’s local magnetic field. Its sensors, called magnetometers, may be placed on the ground surface, in the air, in satellites, or in boreholes beneath the surface of the Earth. For measurements in agricultural fields, magnetometers are typically positioned within a couple of meters of the ground surface. Gradiometers, which are better adapted to emphasize magnetic field anomalies from shallow sources, are set up with two magnetometers mounted a short distance (< 1 m) apart. This arrangement allows the magnetic field gradient between them to be measured (fig. 6-14). Gradiometers have the added advantage of eliminating the need to make corrections for diurnal fluctuations in the magnetic field. Magnetic surveys using gradiometers have successfully found disturbances (e.g., backfilled trenches and excavated areas) in iron-rich soils (Rogers et al., 2005). This suggests the potential use of this technology to identify the extent and location of some anthropogenic soils, particularly in order 1 soil survey applications.
Soil Survey Manual, Ag. Handbook 18, 2017, (p. 377).