Evaluation of the Gamma and Neutron Radiation Scattering and Transmission Methods for Soil Density and Moisture Determination
In order to warrant the accuracy of soil density and moisture data from measurements by means of the gamma and neutron radiation attenuation methods several influencing factors have to be taken into account, for example, the soil hydrogen content, the soil inhomogeneity, the resolution characteristics of the measuring device and the probe travel velocity. Some interpretation concepts, related to the total hydrogen content in soil, are discussed in view of a calibration protocol. An iterative calculation procedure is proposed for the case of saturated soil, especially for the case that local organic content information is lacking. Further, a probe-travel velocity criterion and a possible approach to increase the resolution of a measured density profile are presented. Interpretation problems associated with data from inhomogeneous soil, measured with different devices, are discussed in relation with the difference in spatial averaging characteristics, which influence the significance of the measured quantity.