Improvements in farmland surface roughness measurement by employing a new laser scanner

• This paper analyzes the accuracy of surface roughness (rmsh and cl) from the 2-D surface height dataset measured by the laser scanner.
• The rmsh and cl results derived from a single segment change considerably for the same soil surface. The maximum of the rmsh is about twice the minimum, and the maximum of the cl is about three times the minimum.
• The uncertainties in estimated average surface roughness (rmshm and clm) decrease with the increasing segment number, and a power function exists between the uncertainty (i.e., the relative error) and the number of segment.
• 90% accuracy of estimated surface cl can be achieved for the laser scanner used here, and 95% accuracy for estimated surface rmsh.

Farmland surface roughness is related to the surface root mean square height (rmsh) and surface correlation length (cl), and it is not only an important factor influencing wind and water erosion but also an input parameter for modeling radar backscattering coefficients and the passive microwave brightness temperature. Although these surface roughness parameters are important for soil erosion estimation and land surface parameter retrieval from microwave remote sensing data, their measurement accuracy is limited by the measurement method, instruments used and data preprocessing. To obtain high-precision surface roughness measurements, a laser scanner with spatial measuring range of 400 mm × 600 mm is used to measure the surface height of four test sites with different surface roughness. Based on the surface height data measured using the laser scanner, the effect of segment number on the surface roughness accuracy is analyzed using the random sampling method. The results show that the measurement uncertainties rmshm and clm decrease with increasing segment number. Among all four test sites, 80% and 90% accuracies can be achieved for rmshm and clm, respectively. In addition, the required segment number for the same clm accuracy is found to be related to the degree of surface roughness, but this conclusion does not hold for rmshm. In summary, the accuracy of the surface roughness measured by the laser scanner is greater than 80%, and this scanner is very suitable for field measurements due to its ease of operability and mobility.