DOI: 10.5285/4efaefac-b920-465b-90b9-5390d7fbbd26
title: Meteorological and multi-scale topographic data from survey pole, UAV, TLS and ALS used to analyse glacier aerodynamic roughness on Hintereisferner glacier, Austria, collected August 2018

description: Meteorological variables (wind speed, air temperature and wind direction) were collected using two wind towers. Photogrammetric data were collected using a pole-mounted digital camera and DJI Phantom 3 UAV. LiDAR data collected via terrestrial and airborne laser scanning. Fieldwork carried out at Hintereisferner glacier, in the Otztal Alps region, Tyrol, Austria, from 1-15 August 2018 by Joshua Chambers, Thomas Smith and Mark Smith. Terrestrial laser scan (TLS) data collected by Rudolf Sailer. Airborne laser scan (ALS) data originally from Open Data Austria, see Sailer et al. (2012). One wind tower recorded for the entire study duration, the second was moved to different plots every ~4 days. Photogrammetric data were collected on 8, 10, 11, 12 and 13 August. TLS scans were split into upper- and lower-glacier, and completed on 3, 7, 12 and 16 August. Data were used to examine the relations between glacier aerodynamic roughness and sampling resolution, and to develop a correction factor for roughness derived from coarser resolution data. Fieldwork was funded by an INTERACT Transnational Access grant awarded to Mark Smith under the European Union H2020 Grant Agreement No. 730938. Joshua Chambers is supported by a NERC PhD studentship (NE/L002574/1). Ivana Stiperski was funded by Austrian Science Fund (FWF) grant T781-N32.
description: Instruments were placed at five levels on each tower (~0.3, 0.65, 1.22, 1.79 and 2.32 m above the surface, remeasured at each visit). For each, we used five NRG 40 cup anemometers, one NRG 200P wind vane and five shielded and passively-ventilated Extech RHT10 temperature and humidity loggers. Data were recorded on Campbell CR1000s with a 12 V battery stored at the base of each tower. Wind tower data were processed in MS Excel and then MATLAB. For photogrammetric surveys, camera specifications and survey area geometry were used to calculate the footprint of each image, which determined the distance between images required to achieve 60-80% overlap, and the number of images needed for the survey area. Images were predominantly nadir and followed a regular grid pattern, with an additional ~10% of images taken obliquely (&lt; 20° off nadir). All survey plots were marked out using a regular grid of ground control points (GCPs), the locations of which were recorded using a Leica GS10 differential GPS, with a sub-centimetre mean accuracy for each plot. Data were processed using Agisoft Photoscan Professional Edition Version 1.4.0. Dense point clouds were imported into CloudCompare 2.10 for manual cleaning, and digital elevation models were created using linear interpolation with nearest non-empty neighbours, ensuring a regular grid shape with the top of the grid aligned with the direction of flow (roughly South-North). A permanent in-situ Riegl VZ-6000 TLS was used to survey the majority of the glacier ablation zone using a near-infrared wavelength (1050 nm) suited to snow and ice surfaces (University of Innsbruck, 2020a). The TLS is housed in a climate-controlled container near the summit of "im Hinteren Eis" (46.79586° N, 10.78277° E, 3244 m a.s.l.). The point acquisition rate was approx. 23,000 points per second. Horizontal and vertical spatial resolution was ~0.17 m at 1000 m range, giving a theoretical density of 10 points per m2 mid-glacier, and 2 points per m2 at the head of the accumulation zone and near the terminus (University of Innsbruck, 2020b). Regional (gridded) elevation data were acquired for the entire Austrian Alps at 10 m pixel-1 resolution (Open Data Austria, 2020). This regional product was created by interpolation of 2.5 m ALS data obtained during flights over the Ötztal Alps, Tyrol, from 2006-2012 (Fritzmann et al., 2011; Sailer et al., 2012; Fischer et al., 2015). ALTM 3100 and Gemini ALS sensors were used in the Tyrol area, with an average density of 0.25 points m-1. TLS and ALS data were processed in CloudCompare 2.10.
description: Instrumentation NRG #40 cup anemometers NRG 200P wind vane Extech RHT10 temperature and humidity loggers Campbell CR1000 data loggers Leica GS10 differential GPS DJI Phantom 3 Olympus OMD EM-10 camera Riegl VZ-6000 Terrestrial Laser Scanner (TLS) ALTM 3100 and Gemini Airborne Laser Scanner (ALS) sensors Software Agisoft PhotoScan Professional Edition (version 1.4.0) CloudCompare 2.10 ArcGIS ArcMap 10.6 Matlab R2019b Resolution Small plots: DEMs at resolutions of 0.005, 0.01 and 0.05 m pixel-1 Large/UAV plot surveys: 0.01, 0.05, 0.1, 0.5 and 1 m pixel-1 Glacier-scale TLS/ALS: 5, 10, 20 and 30 m pixel-1
description: Wind speed is ±0.05 m s-1 Wind direction is ±1 % Temperature is ±0.1 °C GPS accuracy &lt;1 cm Photogrammetric 3D root mean square (RMS) error was ±0.03 m and RMS re-projection error was 1.66 pixels (2.6 µm) NoData values used either NaN in Matlab or -32767 as is convention in ArcMap.