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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #258769
Title: A simplified close-range photogrammetric technique for soil erosion assessment

Author
item NOUWAKPO, SAYJRO - Purdue University
item Huang, Chi Hua

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2011
Publication Date: 1/1/2012
Citation: Nouwakpo, S.K., Huang, C. 2012. A simplified close-range photogrammetric technique for soil erosion assessment. Soil Science Society of America Journal. 76(1):70-84.

Interpretive Summary: Advances in digital photography make it simple and convenient to obtain pictures of landscape features. When a pair of photos taken from different positions for the same scene, it is possible to create a stereo view of the landscape feature when these two pictures are merged. This process is called photogrammetry. For soil erosion assessment, photogrammetry can be a very useful tool to track erosion and deposition in an eroding gully channel. In order to have a proper scale in the photogrammetry analysis, reference markers of known coordinates need to be placed. In this research, we developed a procedure to acquire the coordinates of markers without the need of using a standard surveying instrument. This technique uses a frame of known dimension and a level to place the frame in a horizontal position. Using a modified photogrammetry procedure that we developed, we were able to derive the coordinates of the markers. Once we have coordinates of the reference markers, standard photogrammetry is deployed to obtain the geometry of the landscape feature. We compared our technique in the laboratory with a laser scanner and in the field with standard survey instrument. Our results are comparable in accuracy as those derived from laser scanning or surveying. This development eliminates the need to use a survey instrument to assess gully erosion. The impact of this research is that the simplified photogrammetry technique can be deployed to conduct a precise erosion assessment in many parts of the world where the necessary field survey equipment may not be available.

Technical Abstract: A two step photogrammetric technique for soil erosion assessment was proposed in this paper. The method combines a photogrammetric procedure for control points generation in a first step followed by a conventional photogrammetric Digital Elevation Model (DEM) extraction procedure. The performance of the method was assessed in the laboratory and tested in the field to digitize ephemeral gullies. In the accuracy test of the first step of our methodology, we found that the maximum Length Measurement Error (LME) was 3.4x10-3 m while the maximum angular deviation from the vertical or horizontal axes was 0.93°. The maximum error between control points coordinates generated by photogrammetry and those generated by a total station was 0.026 m on the horizontal axes and 0.01 m on the vertical axis. We also found that the sensitivity of digital photogrammetry in detecting soil surface elevation changes was similar to that of a laser scanner when the detection was performed on smooth soil surfaces.