3D-measurement of multiscale soil surface roughness

A 3D-profilometer is used for measuring the surface roughness of bare soil of a ploughed field in Finland and a harrowed field in France. The area of the measured surface of the ploughed field was about 1.5 m x 30 m and the area of the measure surface of the harrowed field was roughly 2.1 m x 145 m. The main purposes of these data sets was to produce very long profiles for multiscale surface roughness analysis and profiles in various azimuthe directions for studying the effect of periodic surfaces. It turned out that bare soil shows multiscale behaviour even upto 145 m. Surfaces with strongly periodic components are best described by dividing them into an ideal periodic part and a random part- The periodic component has to be taken into account in the azimuthal roughness description. The height distributions of single periodic profiles may deviate clearly from the Gaussian distribution, but a bare soil surface consisting of periodic profiles may still come close to Gaussian height distribution, because typically the roughness perpendicular to the dominating periodic component is random.