scholarly journals Multi-decadal (1953–2017) rock glacier kinematics analysed by high-resolution topographic data in the upper Kaunertal, Austria

2021 ◽  
Vol 15 (12) ◽  
pp. 5345-5369
Author(s):  
Fabian Fleischer ◽  
Florian Haas ◽  
Livia Piermattei ◽  
Madlene Pfeiffer ◽  
Tobias Heckmann ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Meteorological Data ◽  
Aerial Photographs ◽  
External Forcing ◽  
Airborne Laser ◽  
Significant Acceleration ◽  
Surface Elevation Change ◽  
Rock Glaciers ◽  
Investigation Period ◽  
Different Characteristics

Abstract. Permafrost is being degraded worldwide due to the change in external forcing caused by climate change. This has also been shown to affect the morphodynamics of active rock glaciers. We studied these changes, depending on the analysis, on nine or eight active rock glaciers, respectively, with different characteristics in multiple epochs between 1953 and 2017 in Kaunertal, Austria. A combination of historical aerial photographs and airborne laser scanning data and their derivatives were used to analyse surface movement and surface elevation change. In general, the studied landforms showed a significant acceleration of varying magnitude in the epoch 1997–2006 and a volume loss to variable degrees throughout the investigation period. Rock glaciers related to glacier forefields showed significantly higher rates of subsidence than talus-connected ones. Besides, we detected two rock glaciers with deviating behaviour and one that showed an inactivation of its terminal part. By analysing meteorological data (temperature, precipitation and snow cover onset and duration), we were able to identify possible links to these external forcing parameters. The catchment-wide survey further revealed that, despite the general trend, timing, magnitude and temporal peaks of morphodynamic changes indicate a slightly different sensitivity, response or response time of individual rock glaciers to fluctuations and changes in external forcing parameters.

scholarly journals Multi-decadal (1953–2017) rock glacier morphodynamics analysed by high-resolution topographic data in the Upper Kauner Valley, Austria

2021 ◽  
Author(s):  
Fabian Fleischer ◽  
Florian Haas ◽  
Livia Piermattei ◽  
Madlene Pfeiffer ◽  
Tobias Heckmann ◽  
...  
Keyword(s):  
Laser Scanning ◽  
General Trend ◽  
Meteorological Data ◽  
Aerial Photographs ◽  
External Forcing ◽  
Airborne Laser ◽  
Significant Acceleration ◽  
Rock Glaciers ◽  
Investigation Period ◽  
Different Characteristics

Abstract. Permafrost is being degraded worldwide due to the change in external forcing caused by climate change. This has also been shown to affect the morphodynamics of active rock glaciers. We studied these changes, depending on the analysis, on nine or eight active rock glaciers with different characteristics in multiple epochs between 1953 and 2017 in Kauner Valley, Austria. A combination of historical aerial photographs and airborne laser scanning data and their derivatives are used to analyse surface movement and 3D displacements. In general, the studied landforms show a significant acceleration of varying magnitude in the epoch 1997–2006 and a volume loss to varying degrees throughout the investigation period. Besides, we detect rock glaciers that show indication of inactivation. By analysing meteorological data (temperature, precipitation and snow cover onset and duration), we are able to identify possible links to these external forcing parameters. The combined investigation of horizontal and vertical 3D displacements shows that these are temporally decoupled on some rock glaciers. The catchment-wide survey further reveals that, despite the general trend, timing, magnitude and temporal peaks of morphodynamic changes indicate a slightly different sensitivity, response or response time of individual rock glaciers to fluctuations and changes in external forcing parameters.

scholarly journals On the potential of very high-resolution repeat DEMs in glacial and periglacial environments

2010 ◽  
Vol 4 (1) ◽  
pp. 53-65 ◽  
Author(s):  
J. Abermann ◽  
A. Fischer ◽  
A. Lambrecht ◽  
T. Geist
Keyword(s):  
High Resolution ◽  
Laser Scanning ◽  
Airborne Lidar ◽  
Primary Data ◽  
Glacier Area ◽  
Airborne Laser ◽  
Multi Temporal ◽  
Rock Glaciers ◽  
Data Source ◽  
Very High

Abstract. The potential of high-resolution repeat DEMs was investigated for glaciological applications including periglacial features (e.g. rock glaciers). It was shown that glacier boundaries can be delineated using airborne LIDAR-DEMs as a primary data source and that information on debris cover extent could be extracted using multi-temporal DEMs. Problems and limitations are discussed, and accuracies quantified. Absolute deviations of airborne laser scanning (ALS) derived glacier boundaries from ground-truthed ones were below 4 m for 80% of the ground-truthed values. Overall, we estimated an accuracy of +/−1.5% of the glacier area for glaciers larger than 1 km2. The errors in the case of smaller glaciers did not exceed +/−5% of the glacier area. The use of repeat DEMs in order to obtain information on the extent, characteristics and activity of rock glaciers was investigated and discussed based on examples.

Inoptimality losses in forest management decisions caused by errors in an inventory based on airborne laser scanning and aerial photographs

2010 ◽  
Vol 40 (12) ◽  
pp. 2427-2438 ◽  
Author(s):  
Md. Nurul Islam ◽  
Mikko Kurttila ◽  
Lauri Mehtätalo ◽  
Timo Pukkala
Keyword(s):  
Input Data ◽  
Laser Scanning ◽  
Basal Area ◽  
Airborne Laser Scanning ◽  
Aerial Photographs ◽  
Stand Age ◽  
Inventory Data ◽  
Airborne Laser ◽  
Mean Diameter ◽  
The Mean

Errors in inventory data may lead to inoptimal decisions that ultimately result in financial losses for forest owners. We estimated the expected monetary losses resulting from data errors that are similar to errors in laser-based forest inventory. The mean loss was estimated for 67 stands by simulating 100 realizations of inventory data for each stand with errors that mimic those in airborne laser scanning (ALS) based inventory. These realizations were used as input data in stand management optimization, which maximized the present value of all future net incomes (NPV). The inoptimality loss was calculated as the difference between the NPV of the optimal solution and the true NPV of the solution obtained with erroneous input data. The results showed that the mean loss exceeded €300·ha–1 (US$425·ha–1) in 84% of the stands. On average, the losses increased with decreasing stand age and mean diameter. Furthermore, increasing errors in the basal area weighted mean diameter and basal area of spruce were found to significantly increase the loss. It has been discussed that improvements in the accuracy of ALS-based inventory could be financially justified.

scholarly journals Potential of Modern Photogrammetry Versus Airborne Laser Scanning for Estimating Forest Variables in a Mountain Environment

2019 ◽  
Vol 11 (6) ◽  
pp. 661 ◽  
Author(s):  
Sami Ullah ◽  
Matthias Dees ◽  
Pawan Datta ◽  
Petra Adler ◽  
Mathias Schardt ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Digital Terrain Model ◽  
Basal Area ◽  
Point Clouds ◽  
Airborne Laser Scanning ◽  
Aerial Photographs ◽  
Data Types ◽  
Viable Option ◽  
Airborne Laser ◽  
Mountain Environment

Digital stereo aerial photographs are periodically updated in many countries and offer a viable option for the regular update of information on forest variables. We compared the potential of image-based point clouds derived from three different sets of aerial photographs with airborne laser scanning (ALS) to assess plot-level forest attributes in a mountain environment. The three data types used were (A) high overlapping pan-sharpened (80/60%); (B) high overlapping panchromatic band (80/60%); and (C) standard overlapping pan-sharpened stereo aerial photographs (60/30%). We used height and density metrics at the plot level derived from image-based and ALS point clouds as the explanatory variables and Lorey’s mean height, timber volume, and mean basal area as the response variables. We obtained a RMSE = 8.83%, 29.24% and 35.12% for Lorey’s mean height, volume, and basal area using ALS data, respectively. Similarly, we obtained a RMSE = 9.96%, 31.13%, and 35.99% and RMSE = 11.28%, 31.01%, and 35.66% for Lorey’s mean height, volume and basal area using image-based point clouds derived from pan-sharpened stereo aerial photographs with 80/60% and 60/30% overlapping, respectively. For image-based point clouds derived from a panchromatic band of stereo aerial photographs (80%/60%), we obtained an RMSE = 10.04%, 31.19% and 35.86% for Lorey’s mean height, volume, and basal area, respectively. The overall findings indicated that the performance of image-based point clouds in all cases were as good as ALS. This highlights that in the presence of a highly accurate digital terrain model (DTM) from ALS, image-based point clouds offer a viable option for operational forest management in all countries where stereo aerial photographs are updated on a routine basis.

scholarly journals Thinning of the Monte Perdido Glacier in the Spanish Pyrenees since 1981

2016 ◽  
Vol 10 (2) ◽  
pp. 681-694 ◽  
Author(s):  
Juan Ignacio López-Moreno ◽  
Jesús Revuelto ◽  
Ibai Rico ◽  
Javier Chueca-Cía ◽  
Asunción Julián ◽  
...  
Keyword(s):  
Mass Balance ◽  
Laser Scanning ◽  
Airborne Lidar ◽  
Surface Elevation ◽  
Aerial Photographs ◽  
Climate Data ◽  
Elevation Change ◽  
Factors Affecting ◽  
Digital Elevation ◽  
Surface Elevation Change

Abstract. This paper analyzes the evolution of the Monte Perdido Glacier, the third largest glacier in the Pyrenees, from 1981 to the present. We assessed the evolution of the glacier's surface area by analysis of aerial photographs from 1981, 1999, and 2006, and changes in ice volume by geodetic methods with digital elevation models (DEMs) generated from topographic maps (1981 and 1999), airborne lidar (2010) and terrestrial laser scanning (TLS, 2011, 2012, 2013, and 2014) data. We interpreted the changes in the glacier based on climate data from nearby meteorological stations. The results indicate that the degradation of this glacier accelerated after 1999. The rate of ice surface loss was almost three times greater during 1999–2006 than during earlier periods. Moreover, the rate of glacier thinning was 1.85 times faster during 1999–2010 (rate of surface elevation change  = −8.98 ± 1.80 m, glacier-wide mass balance  = −0.73 ± 0.14 m w.e. yr−1) than during 1981–1999 (rate of surface elevation change  = −8.35 ± 2.12 m, glacier-wide mass balance  = −0.42 ± 0.10 m w.e. yr−1). From 2011 to 2014, ice thinning continued at a slower rate (rate of surface elevation change  = −1.93 ± 0.4 m yr−1, glacier-wide mass balance  = −0.58 ± 0.36 m w.e. yr−1). This deceleration in ice thinning compared to the previous 17 years can be attributed, at least in part, to two consecutive anomalously wet winters and cool summers (2012–2013 and 2013–2014), counteracted to some degree by the intense thinning that occurred during the dry and warm 2011–2012 period. However, local climatic changes observed during the study period do not seem sufficient to explain the acceleration of ice thinning of this glacier, because precipitation and air temperature did not exhibit statistically significant trends during the study period. Rather, the accelerated degradation of this glacier in recent years can be explained by a strong disequilibrium between the glacier and the current climate, and likely by other factors affecting the energy balance (e.g., increased albedo in spring) and feedback mechanisms (e.g., heat emitted from recently exposed bedrock and debris covered areas).

scholarly journals Airborne Laser Scanning and Image Processing Techniques for Archaeological Prospection

2014 ◽  
Vol XL-5 ◽  
pp. 231-235 ◽  
Author(s):  
M. Faltýnová ◽  
P. Nový
Keyword(s):  
Image Processing ◽  
Laser Scanning ◽  
Average Density ◽  
Airborne Laser Scanning ◽  
Aerial Photographs ◽  
Processing Methods ◽  
Archaeological Prospection ◽  
Airborne Laser ◽  
Visualization Techniques ◽  
Shaded Relief

Aerial photography was, for decades, an invaluable tool for archaeological prospection, in spite of the limitation of this method to deforested areas. The airborne laser scanning (ALS) method can be nowadays used to map complex areas and suitable complement earlier findings. This article describes visualization and image processing methods that can be applied on digital terrain models (DTMs) to highlight objects hidden in the landscape. Thanks to the analysis of visualized DTM it is possible to understand the landscape evolution including the differentiation between natural processes and human interventions. Different visualization methods were applied on a case study area. A system of parallel tracks hidden in a forest and its surroundings – part of old route called "Devil's Furrow" near the town of Sázava was chosen. The whole area around well known part of Devil's Furrow has not been prospected systematically yet. The data from the airborne laser scanning acquired by the Czech Office for Surveying, Mapping and Cadastre was used. The average density of the point cloud was approximately 1 point/m<sup>2</sup> The goal of the project was to visualize the utmost smallest terrain discontinuities, e.g. tracks and erosion furrows, which some were not wholly preserved. Generally we were interested in objects that are clearly not visible in DTMs displayed in the form of shaded relief. Some of the typical visualization methods were tested (shaded relief, aspect and slope image). To get better results we applied image-processing methods that were successfully used on aerial photographs or hyperspectral images in the past. The usage of different visualization techniques on one site allowed us to verify the natural character of the southern part of Devil’s Furrow and find formations up to now hidden in the forests.

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