UAV DIGITAL PHOTOGRAMMETRIC ANALYSIS FOR SOIL EROSION EVALUATION IN THE RIVO CATCHMENT: PRELIMINARY RESULTS

Soil erosion is one of the main factors responsible for land degradation in nature. Its quantification in field conditions is very difficult. Here we present the development of a simple, sensitive and inexpensive field method for the quantification of soil loss. The goal is to produce high precision digital elevation models (DEMs) of the soil surface that is investigated repeatedly (after days, months, years, events). The volumetric quantification of soil erosion will be the result of DEM overlapping over time. According to the developed methodological procedure, high-resolution aerial images are acquired by a small unmanned aerial vehicle (UAV) flying at low altitude (15 meters) on test areas smaller than 2 hectares to assure a very high image resolution. For each test area, at least four, homogenously distributed GCPs (Ground Control Points) are measured with GPS for geo-referencing. The images are processed with methods from photogrammetry and computer vision; the structure from motion (SfM) software is applied for this purpose. The results show the validity of the method for the calculation of volumes eroded in rills and gullies, but not so when there is only sheet-washing.