Earth Surface Processes and Landforms · 2015 · 306 citations · 62 references
EngineeringGeomorphologyTerrestrial Laser ScanningGeospatial TechnologySoil Erosion MonitoringQuantitative GeomorphologyLand DegradationPhysical GeographyEarth ScienceSocial SciencesGeospatial MappingExperimental PlotsGeographic Information SciencesExperimental LandscapesLandscape ProcessesSurveyingGeographySub‐humid BadlandsGeologyExtensive Tls DataHillslope ProcessSoil ErosionExperimental GeomorphologyGeomorphic ProcessRemote SensingApplied Geomorphology
Advances in surveying technology now allow high‑resolution topographic mapping of experimental plots (<10 m²), but the representativeness of such small plots remains limited. This study uses Structure‑from‑Motion and Multi‑View Stereo to validate their accuracy against total station and TLS data across three nested scales—from plots (<30 m²) to a 4,710 m² catchment within a 1 km² eroding badland landscape. SfM surveys from multiple platforms were evaluated for topography, sub‑grid roughness, and annual change‑detection capability. Oblique ground‑based SfM yields TLS‑level quality at plot scale but degrades over larger, complex terrain; aerial SfM quality declines with range, with vertical imagery doming effects mitigated by a gyrocopter survey at 50 m altitude, and for soil‑erosion monitoring SfM matches TLS only within ~5 m, best limited to 10–20 m, with RMSE increasing roughly 1:639 per meter of survey range and validation method influencing quality. © 2015 John Wiley & Sons, Ltd.
Abstract In the last decade advances in surveying technology have opened up the possibility of representing topography and monitoring surface changes over experimental plots (<10 m 2 ) in high resolution (~10 3 points m ‐1 ). Yet the representativeness of these small plots is limited. With ‘Structure‐from‐Motion’ (SfM) and ‘Multi‐View Stereo’ (MVS) techniques now becoming part of the geomorphologist's toolkit, there is potential to expand further the scale at which we characterise topography and monitor geomorphic change morphometrically. Moving beyond previous plot‐scale work using Terrestrial Laser Scanning (TLS) surveys, this paper validates robustly a number of SfM‐MVS surveys against total station and extensive TLS data at three nested scales: plots (<30 m 2 ) within a small catchment (4710 m 2 ) within an eroding marl badland landscape (~1 km 2 ). SfM surveys from a number of platforms are evaluated based on: (i) topography; (ii) sub‐grid roughness; and (iii) change‐detection capabilities at an annual scale. Oblique ground‐based images can provide a high‐quality surface equivalent to TLS at the plot scale, but become unreliable over larger areas of complex terrain. Degradation of surface quality with range is observed clearly for SfM models derived from aerial imagery. Recently modelled ‘doming’ effects from the use of vertical imagery are proven empirically as a piloted gyrocopter survey at 50m altitude with convergent off‐nadir imagery provided higher quality data than an Unmanned Aerial Vehicle (UAV) flying at the same height and collecting vertical imagery. For soil erosion monitoring, SfM can provide data comparable with TLS only from small survey ranges (~5 m) and is best limited to survey ranges ~10–20 m. Synthesis of these results with existing validation studies shows a clear degradation of root‐mean squared error (RMSE) with survey range, with a median ratio between RMSE and survey range of 1:639, and highlights the effect of the validation method (e.g. point‐cloud or raster‐based) on the estimated quality. Copyright © 2015 John Wiley & Sons, Ltd.
62