Anmerkungen:
Diese Datenquelle enthält auch Bestandsnachweise, die nicht zu einem Volltext führen.
Beschreibung:
Electromagnetic (EM) measurement methods oer the great potential to non-invasively and contactlessly obtain geological and hydrological soil properties of the uppermost six meters of the subsurface with an areal resolution in the sub-meter range. The presented work is focused on small-sized frequency domain `electromagnetic induction' (EMI) systems which combine the transmitter (Tx) and receiver (Rx) unit in one portable construction and obtain the apparent electrical conductivity ($\sigma_{a}$) of the sensed soil volume by inducing electrical currents and measuring the responding electromagnetic field. The sensing depth of EMI instruments depends on the sensor conguration and in particular the coil orientation and Tx-Rx separation. In principle, multi-conguration EMI data can be inverted for the electrical conductivity distribution over depth. However, there is a demand for efficient inversion algorithms and high-quality EMI data from different sensing depths to perform such an inversion. Here, a novel one-dimensional global-local inversion approach is implemented which evaluates the mist between EMI data and forward modeled data for a two-layer soil using a L1-norm objective function. The global approach is based on a grid search for reasonable model parameters in combination with the local-sensitivity forward model. The two soil models with the smallest misfit are refined using the (local) simplex search algorithm with the more precise full solution electromagnetic forward model. The algorithm is analyzed using synthetic EMI data. Applying the inversion on quantitative EMI transect data from two commercial devices with eight different sensor configurations results in a two-layer electrical conductivity model with lateral and vertical conductivity changes that are in good agreement with a collocated electrical resistivity tomography data set. To improve the depth-resolution beyond available fixed congurations, a novel EMI prototype system (ElMa1) with customizable sensor-array is developed, containing multiple ...