Wolfgang Sulzer

UAV and TLS for monitoring a creek in an alpine environment, Styria, Austria

ABSTRACT Flood events often endangered and damaged the small town of Oberwölz (Styria, Austria) and its nearby surroundings. In 2011 the last bigger flood occurred. After that, the main watercourse, the Schöttlbach creek, became a centre of a national funded research project. A wide variety of methods were applied together with intra- and extra-universitarian project partners to investigate that creek from a fluvial-geomorphological point of view. Apart from hydrological, meteorological, and geophysical methods, both, terrestrial and airborne remote-sensing techniques were applied. In particular, terrestrial laser scanning data as well as terrestrial and aerial photographs were frequently recorded since 2012. On the one hand the terrestrial monitoring focused on some representative erosion sites to quantify detailed erosion rates. On the other hand recording the sediment catchment output at the flood detention basin was intended. The aerial-based monitoring included three flight campaigns using mainly a fixed-wing unmanned aerial vehicle to cover approximately an area of about 170 ha that corresponds roughly to the major parts of the Schöttlbach creek. The main focus of the study lies on the adequate processing, georeferencing, and qualitative and quantitative comparison of the recorded elevation data. This was primarily done by using structure from motion photogrammetry and geodetic measurements. The resulting point clouds, digital elevation models, and orthophotos allow a visualization and quantification of morphodynamic processes. As a main outcome of this study, the combined usage of the mentioned methods can be seen. In this way, data recording from diverse perspectives is possible and allows a consideration of the varying terrain inclination. In addition, the significance of the resulting data for a geomorphological interpretation was assessed by describing the uncertainties. Beyond that, this methodology meets the need for observation at different scales.

UAS-Based Change Detection of the Glacial and Proglacial Transition Zone at Pasterze Glacier, Austria

Glacier-related applications of unmanned aircraft systems (UAS) in high mountain regions with steep topography are relatively rare. This study makes a contribution to the lack of UAS applications in studying alpine glaciers in the European Alps. We transferred an established workflow of UAS-based change detection procedures to Austria’s largest glacier, the Pasterze Glacier. We focused on a selected part of the glacier tongue and its proglacial vicinity to obtain detailed knowledge of (i) the behavior of a lateral crevasse field, (ii) the evolution of glacier surface structures and velocity fields, (iii) glacier ablation behavior and the current glacier margin, and (iv) proglacial dead ice conditions and dead ice ablation. Based on two UAS flight campaigns, accomplished in 2016 (51 days apart), we produced digital elevation models (DEMs) and orthophotos with a ground sampling distance (GSD) of 0.15 m using Structure-from-Motion (SfM) photogrammetry. Electrical resistivity tomography (ERT) profiling was additionally conducted in the proglacial area. Results indicate distinct changes in the crevasse field with massive ice collapses, rapid glacier recession, surface lowering (mean of −0.9 m), and ice disintegration at the margins, calculated degree day factors on the order of −7 to −11 mm d−1·°C−1 for clean ice parts, and minimal changes of the debris-covered dead ice in the proglacial area. With this contribution we highlight the benefit of UAS in comparison to commonly used terrestrial methods and satellite-related approaches.

High mountain geodata as a crucial criterion of research: case studies from Khumbu Himal (Nepal) and Mount Aconcagua (Argentina)

The present study evaluates the usability of available and low‐cost geodata, including topographic maps, remote sensing and geographic information system (GIS) data, for high mountain research activities. The challenges for geospatial technologies in a high mountain environment are discussed. We present two case studies of high mountain environments in Khumbu Himal and Mount Aconcagua (Argentina/Chile), where the applicability and integration of various geodata sets have been applied. Important topics documented and discussed include topographic accuracy, glacier information extraction, multitemporal investigations, digital elevation model (DEM) and image map generation. The study indicates that accuracy analyses of available geodata are mandatory for achieving the requirements of geoscience research.

Contribution of UAS to the monitoring at the Lärchberg-Galgenwald landslide (Austria)

ABSTRACT In April 2001, a rock fall occurred at the landslide Lärchberg-Galgenwald, Austria. The movement of this landslide has been under observation for decades, but the methods used so far have several disadvantages. This article aims to show that unmanned aerial systems (UAS) provide a reasonable alternative in terms for monitoring the landslide. At the landslide, we focused on the most active area to (i) record changes of the landslide’s surface, (ii) assess the accuracy of the resulting data, (iii) assess whether the number of ground control points (GCPs) could be reduced in subsequent UAS surveys, and (iv) conclude whether UAS-based recording is favourable compared to common terrestrial methods. UAS imagery, acquired under challenging site conditions in November 2015 and May 2016, were processed to digital elevation models and orthophotos with a ground sampling distance of 0.04 m, which should display expected changes of up to ~0.17 m (relating to previously reported movements of up to 30 cm a−1) for the same period of time. Using DEM differencing, we calculated a vertical difference that was in the range of a few centimetres in most cases with only a few localized areas of much larger change. The latter are mainly related to single objects moving such as rock blocks or tree trunks. Apart from that, no general surface elevation lowering (a threshold of 0.27 m was used to distinguish significant from insignificant changes) could be detected. Based on the resulting orthophotos, we calculated vectors of horizontal displacement, which confirmed that the changes are related to single objects and revealed that in upcoming flight campaigns the number of GCPs can be generously reduced with an acceptable loss of positional accuracy. Therefore, the suitability of UAS for expanding the monitoring approaches used at Lärchberg-Galgenwald landslide is described.

Biotope mapping of extensive/intensive grassland supported by Remote Sensing and Mobile GIS in Eastern Styria (Austria)

Abstract Sulzer W., Gspurning J., Magnes M., Pink R., Muick M., Sengl P.: Biotope mapping of extensive/ intensive grassland supported by remote sensing and mobile GIS in Eastern Styria (Austria). Ekológia (Bratislava), Vol. 32, No. 4, p. 335-344, 2013. The paper presents a case study for the application of remote sensing data (ASTER, LAND SAT and RG B orthophotographs) and GIS and methods in the context of biotope/grassland mapping/ monitoring in the Province of Styria (Austria). The range of the applied case study covers the detection of extensive/intensive grassland by techniques of multi-temporal satellite and airborne classification for grassland detection. The methodologies of three topics are discussed in this paper: special intensive used grassland detection, the preparation of a field map, with pre-processed land use polygons, and the description of a conceptual approach for a mobile client/server GIS grassland management and monitoring support system. Although from the legal (Government of Styria) point of view these methodologies cannot be used for the specific biotope mapping purposes, the verified results are showing valuable additional information for the intensive mapping activity during the fieldwork and postprocessing.

Land Use in the Drava Basin: Past and Present

Current land use in the Drava River Basin (DRB) and its recent changes are detected from the data of the CORINE Land Cover (CLC) inventory, which allows a multitemporal analysis for the time period 1990–2012. Further data, like a DEM, were taken from the European Environmental Agency database. In order to provide a good overview, 11 land use classes were defined. Their distribution as well as their changes are shown in maps and analyzed statistically. The most striking results are (i) the clear dominance of the land use class forests (46% of the DRB), (ii) a pronounced differentiation of land use between the eastern and the western part of the catchment, both for natural and cultural reasons, and (iii) a relatively satisfactory environmental status, reflected among others by a high proportion of protected areas.

Natural Hazards and Earth Observation

Hazard always arises from the interplay of social and biological and physical systems; disasters are generated as much or more by human actions as by physical events and there is a proofed impact of global warming on natural disasters. In recent years, Remote Sensing technologies has been of considerable interest concerned with emergency services and disaster management. The objective of this paper is not to provide an overview of how Earth observation technologies can be used in the management of natural hazards in details and in case studies. The focus lies in the documentation of the requirements for the usage of Remote Sensing images within the topics of natural hazards and disaster management on different scales (from global to local aspects). Some examples of international operational mechanisms (Charter, Copernicus, ZKI), serving rapid mapping on Earth observation data will be pointed out.

Detection of land-cover and land-use change in the Hohe Tauern National Park (Austria) using an object-based classification approach: first results

Land-cover and land-use (LCLU) change reflects environmental as well as social changes. High-mountain environments such as the Hohe Tauern Range (Austria) and its National Park are very sensitive to these changes. Remotely sensed data are ideally suited to detect and analyze land-cover and land-use changes on different spatial and temporal scales. In this study a Landsat Thematic Mapper (TM) time-series from 1988 to 2003, aerial photographs and auxiliary GIS data were used detect land-cover and land-use changes in the National Park and its surroundings. The objective of the study was to develop and test a transferable method for change detection in comparable high-mountain environments. After applying a series of pre-processing steps, object-based image analysis, on the basis of Definiens Developer, was used to extracted land-cover and land-use information from the Landsat images. To generate meaningful image objects, a multiresolutions segmentation algorithm was combined with image object merging. The resultant image objects were then classified by using a hierarchically organized classification method. In a further step the resultant outputs of the land-cover and landuse classifications build the basis for the post-classification change detection. Moreover the advantages and disadvantages of the developed method, the first results as well as future adaptations of the method and applications are discussed in this paper.