Testing the utility of structure‐from‐motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion

Abstract

Quantifying the extent of soil erosion at a fine spatial resolution can be time consuming and costly; however, proximal remote sensing approaches to collect topographic data present an emerging alternative for quantifying soil volumes lost via erosion. Herein we compare terrestrial laser scanning (TLS), and both unmanned aerial vehicle (UAV) and ground photography (GP) structurefrom-motion (SfM) derived topography. We compare the cost-effectiveness and accuracy of both SfM techniques to TLS for erosion gully surveying in upland landscapes, treating TLS as a benchmark. Further, we quantify volumetric soil loss estimates from upland gullies using digital surface models derived by each technique and subtracted from an interpolated pre-erosion surface. Soil loss estimates from UAV and GP SfM reconstructions were comparable to those from TLS, whereby the slopes of the relationship between all three techniques were not significantly different from 1:1 line. Only for the TLS to GP comparison was the intercept significantly different from zero, showing that GP is more capable of measuring the volumes of very small erosion features. In terms of costeffectiveness in data collection and processing time, both UAV and GP were comparable with the TLS on a per-site basis (13.4 and 8.2 person-hours versus 13.4 for TLS); however, GP was less suitable for surveying larger areas (127 person-hours per ha À1 versus 4.5 for UAV and 3.9 for TLS). Annual repeat surveys using GP were capable of detecting mean vertical erosion change on peaty soils. These first published estimates of whole gully erosion rates (0.077 m a À1 ) suggest that combined erosion rates on gully floors and walls are around three times the value of previous estimates, which largely characterize wind and rainsplash erosion of gully walls.

Assessment of UAV and Ground-Based Structure from Motion with Multi-View Stereo Photogrammetry in a Gullied Savanna Catchment

“…These results agree with other studies that have used aerial platforms to capture images across large areas in complex terrain (RMSE values ranging from 0.05 m to~1 m [18,36,47,[101][102][103]), and ground-based approaches to model gully systems (RMSE values ranging from 0.025 m to 0.155 m [40][41][42]46,47,49,104,105]). While the overall elevation errors of the UAV topographic models were large relative to a pre-existing airborne LiDAR dataset and RTK validation points, cross-sections extracted from the UAV DSM broadly match the shape of gully profiles, although are vertically offset.…”

Patterns and drivers of peat topographic changes determined from Structure‐from‐Motion photogrammetry at field plot and laboratory scales

“…These values are moderate in comparison with the globally reported Table VI. Glendell et al (2017) used ground photography SfM in 10 upland peat sites distributed across England and Wales to measure erosion. Frost cycles indicate the number of times soil surface temperature fell below 0°C and also returned above 0°C; both have to occur to count as one cycle negative topographic change rates (24 ± 8 mm yr -1 ) measured using erosion pins (Evans and Warburton, 2007;Grayson et al, 2012).…”

Fine-Resolution Repeat Topographic Surveying of Dryland Landscapes Using UAS-Based Structure-from-Motion Photogrammetry: Assessing Accuracy and Precision against Traditional Ground-Based Erosion Measurements

“…Eltner and Schneider [32] reported a 3D RMSE of 9 mm compared to ground check points measured with a total station and 3D RMSE of 8.7 mm compared to terrestrial laser scanning. Glendell et al [73] compared vertically differenced DEMs using terrestrial laser scanning methods against UAS image reconstructions, both with 2 cm GSD. They found vertical difference RSMEs as low as 5 and 6 cm.…”