A Simple Close Range Photogrammetry Technique to Assess Soil Erosion in the Field.

Evaluating the performance of a soil erosion prediction model depends on the ability to accurately measure the gain or loss of sediment in an area. Recent development in acquiring detailed surface elevation data (DEM) makes it feasible to assess soil erosion and deposition spatially.  Digital photogrammetry is one of the methodologies that is becoming widely used to acquire DEMs.  Nevertheless, there are still some limitations in the technique, such as the need to use another surveying instrument to acquire the coordinates of the ground control points (i.e., reference markers) or using a commercial software package to back calculate the coordinates using distances between markers.  To simplify the digital photogrammetry and maintain the accuracy of the DEM, we developed a stable approach to determine the coordinates of the control points without the need of a field survey instrument or commercial software.  We evaluated the accuracy of our technique in determining the XYZ locations of control points. We also compared the DEM produced using the close range photogrammetry technique to a DEM acquired by precision laser scanning.  We also deployed our technique in the field to show its potential in replacing the erosion pin method for soil erosion assessment.