Digital close -range photogrammetry for generation of digital soil surface elevation models: Methodology and applications for soil erosion experiments
Abstract
A digital photogrammetric technique was developed and applied to generate DEMs with high spatial and temporal resolution of soil surfaces. DEMs of a rainfall simulation study in a 4 m by 4 m soil box were produced. The study was prepared to investigate the influence of flow convergence and divergence on soil surfaces with different slope shapes. Five slope shapes with different horizontal and vertical slope components were prepared. The rain was stopped five times and images for DEM generation were acquired after 0, 10, 20, 40, 60, and 90 minutes. Image acquisition took only a couple of minutes. Images were acquired at a scale of 0.9 mm per pixel. DEMs with a ground resolution of 3 mm were produced. Comparing coordinates of overlapping stereo models, vertical precision of the DEMs was determined to be 1.26 mm. The accuracy potential of the camera was tested, and it was determined that DEM precision was limited to camera calibration. Slope shape had significant influence on runoff and sediment yield. The linear-linear (vertical-horizontal slope component) slope produced the most runoff and sediment yield. The concave-linear slope produced significantly less sediment yield than any other slope shape. Self organization of the drainage network on the soil surface followed the theory of minimization of energy expenditure. Drainage density of the final rill network was similar for all slope shapes, indicating that slope shape did not affect drainage density. Divergence and convergence of surface flow caused differences in rill ‘efficiency’. The rather generalized and static representation of soil topography in current soil erosion prediction models does not adequately represent the dynamic changes on the evolving soil surface and drainage system. The photogrammetric methodology was also compared to a new generation of line laser scanner on a 2 m by 4 m flume. DEM resolution was 3 mm. Precisions determined from overlapping DEMs indicated a vertical precision of 1.56 mm for the laser scanner and 1.69 mm for the photogrammetric technique. Precision of the laser scanner was limited by the precision of point measurement in overlapping scans. Precision of the photogrammetric technique was limited by camera calibration.
Degree
Ph.D.
Advisors
Nearing, Purdue University.
Subject Area
Soil sciences
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