Roughness characterization of porous soil using acoustic backscatter

The characterization of soil surface roughness and soil pore properties is important to understanding local soil erodibility. Acoustic techniques can take measurements in situ and have the potential for characterizing the roughness and pore properties of soils rapidly. Previous acoustic techniques, like the probe microphone and the level difference technique, could measure the pore properties and the roughness but not both independently. The previous acoustic techniques examined sound propagated in the forward direction over rough soil surfaces. Acoustic backscatter has been determined to be insensitive to pore properties for typical weathered agricultural soils and sensitive to roughness in both vertical and horizontal scales on the surface. The acoustic backscatter technique gives results for the roughness in terms of two independent parameters, an RMS height and a correlation length for the roughness. Measurements of roughness from soil surfaces were taken with acoustic backscatter and with a laser profiler. The measurements from both the laser profiler and the acoustic technique are presented. The RMS heights and correlation lengths calculated from the acoustic backscatter and laser profiler measurements are then compared. The backscatter technique can then be combined with forward propagation methods to characterize both pore properties and roughness of soil surfaces.