Submitted to: The Photogrammetic Record
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2004
Publication Date: 3/1/2005
Citation: Nearing, M.A., Rieke-Zapp, D. 2005. Digital close range photogrammetry for measurement of soil erosion. The Photogrammetic Record 20(109):69. Interpretive Summary: A method was developed in this experiment to measure the surface elevation of soils in the laboratory to a very high level (within approximately 1/20th of an inch) of accuracy and precision. The method uses digital photos with a high level of precision to create a stereo images of the soil surfaces that can then be used to measure surface elevations. The method was used to precisely measure the changes of a soil under rainfall in order to understand the evolution of the surface as it changes during erosion. The method has promise for use in erosion experiments and for monitoring the rates of erosion in the field. Other methods used in the past, including laser optical methods, have not had the ability to measure very irregular surfaces as this one can. This method may be very important in terms of advancing our understanding of erosion rates and processes, which will lead to better conservation of soil resources.
Technical Abstract: Many of the processes involved in soil erosion have dimensions on the millimetre scale. Modelling and quantification of such processes require information on soil surface topography with adequate resolution. The purpose of this study was to generate Digital Elevation Models (DEMs) from soil surfaces with high spatial and temporal resolution. Digital photogrammetry was applied for measuring erosion rates on complex shaped soil surfaces under laboratory rainfall conditions. A total of 60 DEMs were generated, covering a planimetric area of 16 m². The DEMs had a grid resolution of 3 mm. A vertical precision of approximately 1 mm was desired for DEM analysis. A consumer grade digital camera was used for image acquisition. The camera was calibrated using BLUH software. Homologous points in overlapping images were identified with least squares matching software. Irregularly spaced object coordinates were interpolated to a regular grid in a geographic information system. The resulting DEMs represented the soil surface well. A precision of 1'26 mm in the vertical was attained. The precision of DEM production was limited to camera calibration. Improvements of the presented setup could include the use of better control points and more advanced image matching strategies for identification of homologous points. The DEMs allowed for detailed analysis of soil surface evolution.