A statistical approach for predicting accuracies of soil properties measured by single, double and dual gamma beams |
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| Authors: | T MIYAZAKI T KASUBUCHI S HASEGAWA† |
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| Institution: | Faculty of Agriculture, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Japan;Hokkaido National Agricultural Experiment Station, Japan;National Institute of Agro-Environmental Sciences, Japan |
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| Abstract: | A statistical analysis is developed to describe the accuracies of soil properties measured through single, double and dual gamma-beam methods. The gamma sources are 137Cs for the high-energy beam (662 keV) and 241Am for the low-energy beam (60 keV). The theoretical confidence intervals of the thicknesses or water contents of samples are determined using a modification of the method of Gardner el al. (1972), who derived theoretical variances using standard error propagation formulae. The finding of Gardner et al. that, in the double-beam method, errors in the soil bulk density and water content measurements are primarily caused by random emission from the sources, is confirmed by the theoretical confidence intervals and is applied to the single-beam and dual-beam methods. The effects of interferences between gamma rays in the dual-beam method on the accuracies of estimations are examined. The minimum measurement time to attain a required accuracy can be predicted from the theoretical confidence intervals. |
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