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Title: Quantifying uncertainty in high-resolution remotely sensed topographic surveys for ephemeral gully channel monitoring

Author
item Wells, Robert - Rob
item MOMM, HENRIQUE G - Middle Tennessee State University
item CASTILLO, CAROLOS - Universidad De Cordoba

Submitted to: Earth Surface Dynamics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2017
Publication Date: 7/6/2017
Citation: Wells, R.R., Momm, H., Castillo, C. 2017. Quantifying uncertainty in high-resolution remotely sensed topographic surveys for ephemeral gully channel monitoring. Earth Surface Dynamics. 5:347-367. https://doi.org/10.5194/esurf-5-347-2017.

Interpretive Summary: As technology presents a gateway to finer resolution survey information, caution must be exercised in the evaluation of alignment error and subsequent morphological determinations. Three survey technologies were evaluated: ground-based photogrammetry, un-manned aerial vehicle photogrammetry, and ground-based LiDAR. Given the superiority perception of LiDAR, the photogrammetry technology was compared to LiDAR. Initial project planning, either as temporal or single occupation, effective use of ground control will facilitate alignment and proper morphological conclusions. None of these methods are without limitation and the ultimate goal of the data collection effort should guide the planning phase of the project. Temporal assessment of gully channels and most geomorphic process descriptions can be accomplished with a camera and a few ground control points, whether on the ground or airborne. Each of the survey methods provided herein performed very well and, although the scoring was not very spectacular, the fixed-wing un-manned aerial vehicle data would be satisfactory for most static model evaluations.

Technical Abstract: Spatio-temporal measurements of landform evolution provide the basis for process-based theory formulation and validation. Overtime, field measurement of landforms has increased significantly worldwide, driven primarily by the availability of new surveying technologies. However, there is not a standardized and/or coordinated effort within the scientific community to collect morphological data in a dependable and reproducible manner, specifically when performing long-term small-scale process investigation studies. Measurements of the same site using identical methods and equipment, but performed at different time periods can lead to incorrect estimates of landform change as a result of three-dimensional registration errors. This work evaluated measurements of an ephemeral gully channel located in agricultural land using multiple independent survey techniques for locational accuracy and their applicability to generate information for model development/validation. Terrestrial photogrammetry and un-maned aerial vehicle-based platforms were compared to terrestrial LiDAR, defined herein as the reference dataset. Given the small-scale of the landform measured, alignment and ensemble equivalence between data sources were addressed sine qua non through post-processing. Utilization of ground control points were prerequisite to three-dimensional registration between datasets and improved confidence in the morphology information generated. Not one of the methods were without limitation; however, careful attention to project pre-planning and data nature will ultimately guide temporal efficacy and practicality of management decisions.