Articles | Volume 5, issue 3
Research article
06 Jul 2017
Research article |  | 06 Jul 2017

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

Robert R. Wells, Henrique G. Momm, and Carlos Castillo

Abstract. Spatio-temporal measurements of landform evolution provide the basis for process-based theory formulation and validation. Over time, field measurements of landforms have increased significantly worldwide, driven primarily by the availability of new surveying technologies. However, there is no standardized 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, may 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 on agricultural land using multiple independent survey techniques for locational accuracy and their applicability in generating information for model development and validation. Terrestrial and unmanned aerial vehicle photogrammetry platforms were compared to terrestrial lidar, defined herein as the reference dataset. Given the small scale of the measured landform, the alignment and ensemble equivalence between data sources was addressed through postprocessing. The utilization of ground control points was a prerequisite to three-dimensional registration between datasets and improved the confidence in the morphology information generated. None of the methods were without limitation; however, careful attention to project preplanning and data nature will ultimately guide the temporal efficacy and practicality of management decisions.

Short 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, unmanned aerial vehicle photogrammetry, and ground-based lidar. Initial project planning necessitates the effective use of ground control to facilitate alignment and proper morphological conclusions.