Rapid numerical estimation of soil thermal properties for a broad class of heat-pulse emitter geometries

The recently developed dual-probe heat-pulse technology permits the rapid, automatic monitoring of soil volumetric heat capacity, thermal diffusivity, and conductivity. The method relies on parameter fits of equations describing received pulse shape. These, in turn, depend on the particular geometric model assumed to characterize the sensor system. This paper describes an estimation procedure applicable to a wide class of sensor geometries. Key attributes of the method are that: (1) it replaces multidimensional, parameter space searches with a single, univariate optimization; (2) no derivatives are required for point estimates; (3) except for a one-time-only table precalculation, computational requirements are independent of model complexity; and (4) it computes its own initial estimates from the data. A computer implementation of the method is presented along with fits of finite and infinite line source emitters to temperature data from laboratory dual-probe heat-pulse experiments. The results show the new method gives answers identical to the commonly used Marquardt algorithm.