The potential of small unmanned aircraft systems and structure-from-motion for topographic surveys: a test of emerging integrated approaches at Cwm Idwal, North Wales

Novel topographic survey methods that integrate both structure-from-motion (SfM) photogrammetry and small unmanned aircraft systems (sUAS) are a rapidly evolving investigative technique. Due to the diverse range of survey configurations available and the infancy of these new methods, further research is required. Here, the accuracy, precision and potential applications of this approach are investigated. A total of 543 images of the Cwm Idwal moraine–mound complex were captured from a light (b5 kg) semi-autonomous multi-rotor unmanned aircraft system using a consumer-grade 18 MP compact digital camera. The imageswere used to produce a DSM(digital surfacemodel) of themoraines. The DSMis in good agreement with 7761 total station survey points providing a total verticalRMSE value of 0.517mand verticalRMSE values as lowas 0.200mfor less densely vegetated areas of the DSM. High-precision topographic data can be acquired rapidly using this technique with the resulting DSMs and orthorectified aerial imagery at sub-decimetre resolutions. Positional errors on the total station dataset, vegetation and steep terrain are identified as the causes of vertical disagreement. Whilst this aerial survey approach is advocated for use in a range of geomorphological settings, care must be taken to ensure that adequate ground control is applied to give a high degree of accuracy

Internal structure and significance of ice-marginal moraine in the Kebnekaise Mountains, northern Sweden

Despite a long history of glaciological research, the mode of formation and palaeoenvironmental significance of moraine systems in the Kebnekaise Mountains, Sweden has remained uncertain. These landforms offer the potential to elucidate glacier response prior to the period of direct monitoring and provide an insight into the ice-marginal processes operating at polythermal valley glaciers. This study sets out to test existing interpretations of Scandinavian ice-marginal moraines which invoke ice stagnation, pushing, stacking/dumping, and push-deformation as important moraine forming processes. Moraines at Isfallsglaciären were investigated using ground-penetrating radar to document the internal structural characteristics of the landform assemblage. Radar surveys revealed a range of substrate composition and reflectors, indicating a debris-ice interface and bounding surfaces within the moraine. The moraine is demonstrated to contain both ice-rich and debris-rich zones, reflecting a complex depositional history and a polygenetic origin. As a consequence of glacier overriding, the morphology of these landforms provides a misleading indicator of glacial history. Traditional geochronological methods are unlikely to be effective on this type of landform as the fresh surface may post-date the formation of the landform following reoccupation of the moraine rampart by the glacier. This research highlights that the interpretation of geochronological datasets from similar moraine systems should be undertaken with caution

The potential of small unmanned aircraft systems and structure-from-motion for topographic surveys: a test of emerging integrated approaches at Cwm Idwal, North Wales

This paper was accepted for publication in the journal Geomorphology and the definitive published version is available at http://dx.doi.org/10.1016/j.geomorph.2014.07.021Novel topographic survey methods that integrate both structure-from-motion (SfM) photogrammetry and small unmanned aircraft systems (sUAS) are a rapidly evolving investigative technique. Due to the diverse range of survey configurations available and the infancy of these new methods, further research is required. Here, the accuracy, precision and potential applications of this approach are investigated. A total of 543 images of the Cwm Idwal moraine–mound complex were captured from a light (b5 kg) semi-autonomous multi-rotor unmanned aircraft system using a consumer-grade 18 MP compact digital camera. The imageswere used to produce a DSM(digital surfacemodel) of themoraines. The DSMis in good agreement with 7761 total station survey points providing a total verticalRMSE value of 0.517mand verticalRMSE values as lowas 0.200mfor less densely vegetated areas of the DSM. High-precision topographic data can be acquired rapidly using this technique with the resulting DSMs and orthorectified aerial imagery at sub-decimetre resolutions. Positional errors on the total station dataset, vegetation and steep terrain are identified as the causes of vertical disagreement. Whilst this aerial survey approach is advocated for use in a range of geomorphological settings, care must be taken to ensure that adequate ground control is applied to give a high degree of accuracy

Causes of degradation and erosion of a blanket mire in the southern Pennines, UK

This study investigates the causes of erosion and degradation of March Haigh, a blanket mire in the southern Pennines (UK), over a period of 160 years starting in 1840 AD. Peat samples taken from the site were dated using 210Pb; their humification and magnetic susceptibility were measured; and they were examined for pollen, plant macrofossils and microscopic charcoal. Stratigraphic correlation with a dated ‘master’ sample was achieved using indicators of air pollution (magnetic susceptibility) and climate (peat humification). The data were used in conjunction with documentary records to reconstruct past variations in grazing pressure, climate, moorland fires and air pollution. Three major vegetation changes have occurred on the moorland since 1840, namely: 1) the disappearance of Sphagnum spp. in the mid 19th century; 2) the replacement of Calluna vulgaris by Poaceae as the dominant vegetation type ca. 1918; and 3) a reduction in vegetation cover and consequent erosion ca. 1959. The results concur with the findings of other investigations of ecological change in the southern Pennines insofar as degradation of vegetation prior to the mid 20th century appears to have been caused by air pollution, climate change and fire. Following the removal of vegetation by a severe fire during the summer of 1959, unprecedented sheep stocking levels maintained the bare peat surface and thus precipitated extensive erosion

Blanket peat erosion and sediment yield in an upland reservoir catchment in the southern Pennines, UK

This paper investigates temporal variations in fluxes of peat and other sediment in the catchment of March Haigh Reservoir, West Yorkshire. Long-term estimates of sediment yield were derived from a study of reservoir sediments. Magnetic properties were used to correlate ten cores to a master profile dated using 210Pb and 137Cs. A 14C date suggests that most of the organic component of the sediment is allochthonous and derived from peat eroded from the catchment. Organic sediment yields suggest low catchment erosion rates between 1838 and 1963. Blanket peat erosion increased significantly after 1963, and peaked between 1976 and 1984. Estimates of total sediment yield range between 2 and 28 t km-2 a-1. These yields are significantly lower than those from some previous studies examining reservoir sedimentation in other blanket peat-covered catchments. The low yield estimates may be due to relatively low rates of erosion in the basin, but may also be partly explained by maintenance of silt traps during the early life of the reservoir and removal of sediment by scouring. Sedimentation within the reservoir is spatially variable, and bathymetry and sediment source appear to be the dominant controls on sedimentation patterns within the reservoir

Runoff and sediment production in blanket peat moorland studies in the Southern Pennines

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