Manchester Geographical Society

North West Geography


Volume 19, Number 2, 2019

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Toward a protocol for UAV surveying in Environmental Sciences

The use of small unmanned aerial vehicles (sUAV) has significantly enriched surveying in the environmental sciences within the last few years, due partly in technological advances in onboard GPS and more predominantly with associated ease of post-processing using photogrammetric software such as structure from motion. In addition, the use of sUAV photography to generate 3D elevation models of objects and landscapes at high resolutions has proved an easily accessible alternative to often expensive, cumbersome laser scanning systems. Survey spatial coverage can be increased simply through an increase in flight altitude, although resolution is sacrificed, however finding a balance between these two factors is key to producing high quality data, quickly, yet to date a protocol for deployment of UAVs to establish optimal spatial coverage, flight height to resolution ratio, and ground control point spacing, remains missing in the literature. Here, we establish a simple, repeatable methodology, to provide users with knowledge of how to optimize flight plans accordingto their requirements for resolution and coverage and best practice processing options are detailed to for the generation of orthomosaics and 3D digital elevation models at a variety of resolutions.

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Glaciation of the English Lake District during the Late-glacial: a new analysis using 10Be and Schmidt hammer exposure dating

Recalibration of published 10Be ages from the classic cirque moraines at Keskadale, Lake District, in combination with calibrated relative ages provided by Schmidt hammer exposure dating (SHED) in the nearby Ling Comb cirque, provide new insights into the extent and retreat history of glaciers during the Late-glacial interval (14.7–11.7 ka). Based on a globallycalibrated production rate, glacial surfaces at Keskadale return exposure ages of 12.3 ± 1.1 ka (lower moraine) and 12.5 ± 1.0 ka (upper cirque threshold), both within the Younger Dryas. A new 10Be age of 8.6 ± 0.9 ka is reported from a boulder from the lower moraine crest which may reflect post-depositional exhumation, erosion or instability. Alternative locally-calibrated production rates from Scotland produce 10Be ages that are up to ~8% older and push the oldest exposure ages to the Allerød-Younger Dryas boundary. At Ling Comb, ~4 km from Keskadale, granitic moraine boulders return calibrated relative ages which span the last glacial-interglacial transition, but these vary by ~6% depending on the choice of production rate. As post-depositional erosion of moraines can profoundly influence the distribution of boulder exposure ages, these data are interpreted as minimum limiting ages, with moraine deposition constrained conservatively to between 11.6 ± 1.3 ka and 12.3 ± 1.4 ka. While lithological and geomorphological processes, in combination with production rate uncertainty, complicate interpretation of these datasets, these data appear consistent with Younger Dryas glaciation of Lake District cirques.

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