Permanent Terrestrial Laserscanner "Im hinteren Eis"
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Brief summary
| Location | Rofental, Ötztal Alps close to summit "Im hinteren Eis" (3270 m a.s.l.) (Container: 46°47'45.10" / 10°46'57.65") |
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| Instrumentation | Terrestrial Laserscanner (Riegl VZ-6000) Range up to 6 km, Wavelength 1050 nm - perfect for ice and snow
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| Aim | Precise measurements of surface changes for glaciological and geomorphological applications with
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| Partner | University of Innsbruck
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| Funding | University of Innsbruck, Austria Austrian Federal Ministry of Science, Research and Economy (BMWFW) |
Location
Close to summit "Im hinteren Eis" (approx. 3200 m a.s.l.) above the orographic right side of Hintereisferner, Ötztal Alps, Tyrol (see Figure 1) a measurement site which includes a terrestrial laser scanner (TLS) was instrumented in autumn 2016. Additionally, a fully equipped automatic weather station (AWS) with an extended instrumentation (e.g. 6 m tower for flux-measurements at different levels) is installed very close to the TLS position. The basic set-up foresees the installation of additional components.
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Aim
The aim of the TLS measurements is to repeatedly measure volume changes of Hintereisferner with a high temporal and spatial resolution to make substantial contributions to the exploration of the mass budget of Hintereisferner and associated processes (e.g. snow re-distribution by wind, avalanches) as well as the understanding of the dynamics of alpine type glaciers. The measurements also offer the opportunity to quantify and analyse geomorphological and glacio-morphological processes in the vicinity of the glacier. Furthermore, it is intended to pass the measurements and the respective analysis on to process modelling groups as high resolution validation data (e.g. avalanche modelling).
Instrumentation
The installed TLS is a long-range Riegl VZ-6000 (www.riegl.com) scanner with the optimal wavelength for observing snow and ice surfaces. The main features of the VZ-6000 are:
- Range: 6000 m
- Wavelength: 1050 nm
- Field of View: 60° vertical, 360 ° horizontal
- Measurements per second: 23000 to 222000
- Beam divergence: 0.12 mrad (~ 0.12 m @ 1000 m)
- Temperature range measurements: -10°C to +50°C
- -"- (without Protective Housing): -20°C, if TLS is in use
- Integrated camera: 2560x1920 pixels
The VZ-6000 laser scanner ‚Im hinteren Eis’ is placed in a standard container, which also hosts computers and other instruments, and protected by a special so-called Protective Housing (see Figure 2). The power supply to the AWS and the container is via a mains power line from the nearby ski resort Schnalstaler Gletscherbahnen.
Set-up status
At the moment (autumn 2017), the irregular scans are conducted with a horizontal field of view of 120° and a vertical on of 60° (see Figure 3 ). The horizontal and vertical frame resolutions are in the order of 0.01° (~0.17 m @ 1000 m). According to that the center part of the glacier tongue is captured by approx. 10 points/m2 and the accumulation area of Hintereisferner by approx. 2 points/m2.
Expected accuracy of the TLS measurements
Analysis of the measurements already conducted yield very low (< 0.15 m) deviation of the TLS data against Airborne Laserscanning (ALS) data in stable areas, where no surface changes are to be expected from geomorphological activity. The relative deviations of the TLS scans to each other are < 0.10 m.
A short illustration of the measurements of the first campaigns
The TLS measurements contribute substantially to the Hintereisferner mass balance (winter and summer balances) calculations (see Figure 4). The visible bias between the TLS and glaciological mass balance profiles are the expected result of glacier dynamics, and corresponds very well with the research results of the that have been gained on base of ALS campaigns. Hence, it can be stated that the TLS data derived from the station ‚Im hinteren Eis’ are able to contribute substantially to the analysis of the dynamic behaviour of alpine type glaciers.
As mentioned above, the TLS data could also be used for the analysis of processes that occur in the vicinity of Hintereisferner. Exemplarily an avalanche that occurred in Winter 2016/17 is shown below. The avalanche release zone as well as the erosion/entrainment zone and the avalanche deposits are clearly visible in Figure 5. The capability for the detection of such phenomena based on TLS data for the evaluation of avalanche simulation models is in progress.
