scholarly journals Evaluating Elevation Change Thresholds between Structure-from-Motion DEMs Derived from Historical Aerial Photos and 3DEP LiDAR Data

2020 ◽  
Vol 12 (10) ◽  
pp. 1625
Author(s):  
Peter Chirico ◽  
Jessica DeWitt ◽  
Sarah Bergstresser
Keyword(s):  
Structure From Motion ◽  
Three Dimensional ◽  
The United States ◽  
Aerial Images ◽  
Elevation Change ◽  
Aerial Photos ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Vertical Accuracy ◽  
Accuracy Assessments

This study created digital terrain models (DTMs) from historical aerial images using Structure from Motion (SfM) for a variety of image dates, resolutions, and photo scales. Accuracy assessments were performed on the SfM DTMs, and they were compared to the United States Geological Survey’s three-dimensional digital elevation program (3DEP) light detection and ranging (LiDAR) DTMs to evaluate geomorphic change thresholds based on vertical accuracy assessments and elevation change methodologies. The results of this study document a relationship between historical aerial photo scales and predicted vertical accuracy of the resultant DTMs. The results may be used to assess geomorphic change thresholds over multi-decadal timescales depending on spatial scale, resolution, and accuracy requirements. This study shows that if elevation changes of approximately ±1 m are to be mapped, historical aerial photography collected at 1:20,000 scale or larger would be required for comparison to contemporary LiDAR derived DTMs.

Pan-arctic glaciers volume changes over 1975-2019

2021 ◽  
Author(s):  
Amaury Dehecq ◽  
Alex Gardner ◽  
Romain Hugonnet ◽  
Joaquin Belart
Keyword(s):  
Canadian Arctic ◽  
Aerial Images ◽  
The Arctic ◽  
Glacier Mass Balance ◽  
Russian Arctic ◽  
Elevation Change ◽  
Volume Changes ◽  
Arctic Regions ◽  
Digital Elevation

<p>Glaciers retreat contributed to about 1/3 of the observed sea level rise since 1971 (IPCC). However, long term estimates of glaciers volume changes rely on sparse field observations and region-wide satellite observations are available mostly after 2000. The now declassified images from the American reconnaissance satellite series Hexagon (KH-9), that acquired 6 m resolution stereoscopic images from 1971 to 1986, open new possibilities for glaciers observation.</p><p>Based on recently published methodology (Dehecq et al., 2020, doi: 10.3389/feart.2020.566802), we process all available KH-9 images over the Arctic (Canadian arctic, Iceland, Svalbard, Russian arctic) to generate Digital Elevation Models (DEMs) and ortho-images for the period 1974-1980. We validate the KH-9 DEMs over Iceland against elevation derived from historical aerial images acquired within a month from the satellite acquisition.</p><p>Finally, we calculate the glacier elevation change between the historical DEMs and modern elevation obtained from a time series of ASTER stereo images and validated against ICESat-2 elevation. The geodetic glacier mass balance is calculated for all pan-Arctic regions and analyzed with reference to the last 20 years evolution.</p>

New evidence of glacier surges in the Central Andes of Argentina and Chile

2018 ◽  
Vol 42 (6) ◽  
pp. 792-825 ◽  
Author(s):  
Daniel Falaschi ◽  
Tobias Bolch ◽  
Maria Gabriela Lenzano ◽  
Takeo Tadono ◽  
Andrés Lo Vecchio ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Remote Sensing Data ◽  
Central Andes ◽  
Aerial Images ◽  
Mountain Ranges ◽  
The Andes ◽  
Digital Elevation ◽  
Heterogeneous Behavior ◽  
Elevation Changes ◽  
Glacier Surges

In contrast to the large surge-type glacier clusters widely known for several mountain ranges around the world, the presence of surging glaciers in the Andes has been historically seen as marginal. The improved availability of satellite imagery during the last years facilitates investigating of glaciers in more detail even in remote areas. The purpose of the study was therefore to revisit existing information about surge-type glaciers for the Central Andes of Argentina and Chile (32° 40′–34° 20′ S), to identify and characterize possible further surge-type glaciers, providing new insights into the mass balance and evolution of the velocity of selected glaciers during the surge phase. Based on the analysis of 1962–2015 satellite imagery, historical aerial images, differencing of digital elevation models and a literature survey, we identified 21 surge-type glaciers in the study area. Eleven surge events and six possible surge-type glaciers were identified and described for the first time. The estimation of annual elevation changes of these glaciers for the 2000–2011 period, which encompasses the latest surge events in the region, showed heterogeneous behavior with strongly negative to positive surface elevation change patterns (−1.1 to +1.0 m yr−1). Additionally, we calculated maximum surface velocities of 3±1.9 m d−1 and 3.1±1.1 m d−1 for two of the glaciers during the latest identifiable surge events of 1985–1987 and 2003–2007. Within this glacier cluster, highly variable advance rates (0.01–1 km yr−1) and dissimilar surface velocities at the surge peak (3–35 m d−1) were observed. In comparison with other clusters worldwide, surge-type glaciers in the Central Andes are on average smaller and show minor absolute advances. Generally low velocities and the heterogeneous duration of the surge cycles are common between them and glaciers in the Karakorum, a region with similar climatic characteristics and many known surge-type glaciers. As a definitive assertion concerning the underlying surge mechanism of surges in the Central Andes could not be drawn based on the remote sensing data, this opens more detailed research avenues for surge-type glaciers in the region.

scholarly journals Pluri-decadal (1955–2014) evolution of glacier–rock glacier transitional landforms in the central Andes of Chile (30–33° S)

2017 ◽  
Vol 5 (3) ◽  
pp. 493-509 ◽  
Author(s):  
Sébastien Monnier ◽  
Christophe Kinnard
Keyword(s):  
Feature Tracking ◽  
Central Andes ◽  
Image Feature ◽  
Rock Glacier ◽  
Aerial Photos ◽  
Surface Displacements ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Elevation Model ◽  
Displacement Patterns

Abstract. Three glacier–rock glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955–2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the rock glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of rock glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered glacier areas with large heaving or lowering up to more than ±1 m yr−1. The use of image feature tracking highlighted spatially coherent flow vector patterns over rock glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr−1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, rock glaciers can develop upward at the expense of debris-covered glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and rock glacier development phases. The other landform is a small debris-covered glacier having evolved into a rock glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere against climate change.

scholarly journals Glacial changes of five southwest British Columbia icefields, Canada, mid-1980s to 1999

2008 ◽  
Vol 54 (186) ◽  
pp. 469-478 ◽  
Author(s):  
Jeffrey A. VanLooy ◽  
Richard R. Forster
Keyword(s):  
British Columbia ◽  
Satellite Images ◽  
Surface Elevation ◽  
Interferometric Synthetic Aperture Radar ◽  
Elevation Change ◽  
Glacier Terminus ◽  
M 10 ◽  
Digital Elevation ◽  
Surface Elevation Change ◽  
Elevation Changes

AbstractThis study adjusts and compares digital elevation models (DEMs) created from photogrammetric and interferometric synthetic aperture radar techniques to determine volume and surface elevation changes of five icefields in a remote region of southwest British Columbia, Canada, between the mid-1980s and 1999. Preliminary differences between the DEMs in ice-free and vegetation-free areas indicated variable elevation offsets with increasing altitude (11 m km−1) and with increasing slope (2.7 m (10°)−1). Results indicate a surface elevation change of −6.0 ± 2.7 m (−0.5 ± 0.2 m a−1) and a total volume loss of −19.4 ± 8.8 km3 (−1.5 ± 0.7 km3 a−1), which represents a potential sea-level rise contribution of 0.004 ± 0.002 mm a−1. Temperature and snowfall data from four nearby meteorological stations indicate that increased temperatures and decreased snowfall throughout the late 1980s and 1990s are a likely cause of the thinning. Glacier terminus positions were compared between a historical map (1927) and satellite images (1974, 1990/91 and 2000/01). All observed glaciers were in retreat between 1927 and 1974, as well as between 1990/91 and 2000/01, but many glaciers advanced or significantly slowed in their retreat between 1974 and 1990/91.

scholarly journals Elevation changes of glaciers revealed by multitemporal digital elevation models calibrated by GPS survey in the Khumbu region, Nepal Himalaya, 1992-2008

2012 ◽  
Vol 58 (210) ◽  
pp. 648-656 ◽  
Author(s):  
Takayuki Nuimura ◽  
Koji Fujita ◽  
Satoru Yamaguchi ◽  
Rishi R. Sharma
Keyword(s):  
Digital Elevation Models ◽  
Weighted Least Squares ◽  
High Mountain ◽  
Elevation Change ◽  
Remotely Sensed Data ◽  
Differential Gps ◽  
Nepal Himalaya ◽  
Gps Survey ◽  
Digital Elevation ◽  
Elevation Changes

AbstractDue to remoteness and high altitude, only a few ground-based glacier change studies are available in high-mountain areas in the Himalaya. However, digital elevation models based on remotely sensed data (RS-DEMs) provide feasible opportunities to evaluate how fast Himalayan glaciers are changing. Here we compute elevation changes in glacier surface (total area 183.3 km2) in the Khumbu region, Nepal Himalaya, for the period 1992-2008 using multitemporal RS-DEMs and a map-derived DEM calibrated with differential GPS survey data in 2007. Elevation change is calculated by generating a weighted least-squares linear regression model. Our method enables us to provide the distribution of uncertainty of the elevation change. Debris-covered areas show large lowering rates. The spatial distribution of elevation change shows that the different wastage features of the debris-covered glaciers depend on their scale, slope and the existence of glacial lakes. The elevation changes of glaciers in the eastern Khumbu region are in line with previous studies. The regional average mass balance of -0.40 ± 0.25 m w.e.a-1 for the period 1992-2008 is consistent with a global value of about -0.55 m w.e. a-1 for the period 1996-2005.

scholarly journals Research on colorized physical terrain modeling for intelligent vehicle navigation

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878741
Author(s):  
Jingbin Hao ◽  
Hansong Ji ◽  
Hao Liu ◽  
Zhongkai Li ◽  
Haifeng Yang
Keyword(s):  
Digital Elevation Model ◽  
Land Use Planning ◽  
Three Dimensional ◽  
Aerial Images ◽  
Surface Model ◽  
File Format ◽  
Terrain Model ◽  
Digital Elevation ◽  
Model File ◽  
Elevation Model

Colorized physical terrain models are needed in many applications, such as intelligent navigation, military strategy planning, landscape architecting, and land-use planning. However, current terrain elevation information is stored as digital elevation model file format, and terrain color information is generally stored in aerial images. A method is presented to directly convert the digital elevation model file and aerial images of a given terrain to the colorized virtual three-dimensional terrain model, which can be processed and fabricated by color three-dimensional printers. First, the elevation data and color data were registered and fused. Second, the colorized terrain surface model was created by using the virtual reality makeup language file format. Third, the colorized three-dimensional terrain model was built by adding a base and four walls. Finally, the colorized terrain physical model was fabricated by using a color three-dimensional printer. A terrain sample with typical topographic features was selected for analysis, and the results demonstrated that the colorized virtual three-dimensional terrain model can be constructed efficiently and the colorized physical terrain model can be fabricated precisely, which makes it easier for users to understand and make full use of the given terrain.

scholarly journals Knud Rasmussen Glacier Status Analysis Based on Historical Data and Moving Detection Using RPAS

2021 ◽  
Vol 11 (2) ◽  
pp. 754
Author(s):  
Karel Pavelka ◽  
Jaroslav Šedina ◽  
Karel Pavelka
Keyword(s):  
Three Dimensional ◽  
Image Data ◽  
Point Clouds ◽  
Multiscale Model ◽  
Satellite System ◽  
Flow Speed ◽  
Middle Part ◽  
Google Earth ◽  
Aerial Images ◽  
Aerial Photos

This article discusses partial results of an international scientific expedition to Greenland that researched the geography, geodesy, botany, and glaciology of the area. The results here focus on the photogrammetrical results obtained with the eBee drone in the eastern part of Greenland at the front of the Knud Rasmussen Glacier and the use of archive image data for monitoring the condition of this glacier. In these short-term visits to the site, the possibility of using a drone is discussed and the results show not only the flow speed of the glacier but also the shape and structure from a height of up to 200 m. From two overflights near the glacier front at different times, it was possible to obtain the speed of the glacier flow and the distribution of velocities in the glacier stream. The technology uses a comparison of two point clouds derived from a set of aerial photos taken with the eBee drone, and calculating the M3C2 (Multiscale Model-to-Model Cloud Comparison) distances with CloudCompare software. The results correlate with other measurement methods like accurate and long-term measurement with Global Navigation Satellite System (GNSS), satellite radar, or ground geodetical technology. The resulting speed from the drone data reached in the middle part of the glacier, was approximately 12–15m per day. The second part of the paper focuses on the analysis of modern satellite images of the Knud Rasmussen Glacier from Google Earth (Landsat series 1984–2016) and Sentinel 2a, and a comparison with historical aerial images from 1932 to 1933. Historical images were processed photogrammetrically into a three-dimensional (3D) model. Finally, orthogonalized image data from three systems (drone photos, historical aerial photos, and satellite data) were compared in the ArcGIS software. This allows us to analyze glacier changes over time in the time span from 1932 to 2020, with the caveat that from 1933 to 1983 we did not have data at our disposal. The result shows that more significant changes in the area of this glacier occurred after 2011. The main aim of this article is to research the use of photogrammetric methods for monitoring the condition and parameters of glaciers based on non-traditional technology, such as drones or new processing of historical photos.

Erodibility of vertically exposed salt marsh sediments

2020 ◽  
Author(s):  
Olivia Shears ◽  
Iris Möller ◽  
Tom Spencer ◽  
Katherine Royse ◽  
Ben Evans
Keyword(s):  
Salt Marsh ◽  
Structure From Motion ◽  
Salt Marshes ◽  
Tidal Flat ◽  
Three Dimensional ◽  
The United States ◽  
Small Scale ◽  
External Forcing ◽  
Marsh Sediments

<p>Salt marshes are valuable habitats, providing natural coastal protection. However, change in the extent of salt marsh habitats is occurring globally; regional hotspots include widespread losses in Northwest Europe. These lateral losses are occurring despite relative stability in the vertical dimension (i.e. surface elevation and its relation to rising sea levels). Whilst there are an increasing number of studies reporting and quantifying salt marsh losses, the understanding of what controls lateral marsh dynamics remains weak.</p><p>Numerical models and large-scale experimentation (e.g. in wave flumes) have, to a degree, improved understanding of the mechanisms by which salt marshes can change in the lateral dimension. However, empirical field evidence exploring the role of specific marsh properties and exposure characteristics is lacking. What biophysical factors (i.e. vegetation and sediment characteristics) control internal marsh substrate stability, and how do these factors influence the vulnerability of lateral marsh margins to external forcing?</p><p>The three-dimensional biophysical response of salt marsh substrates to external forcing representative of tidal flat conditions has been investigated. Intertidal sediment sections were extracted from two contrasting UK salt marsh sites: clay-silt rich Tillingham Marsh, Essex, Southeast England, and sand-dominated Warton Marsh, Morecambe Bay, Northwest England. Vertical sections of sediment were exposed to in-situ external forcing conditions on the fronting tidal flat at Tillingham Marsh. Structure-from-motion digital photogrammetry was used to quantify volumetric and structural changes on the vertical faces of the exposed sedimentary cores at approximately 14-day intervals. Three-dimensional structure-from-motion models were analysed alongside empirical water level measurements and meteorological data. Greater loss of material, typically around root structures, characterised the upper section of the sediment core from Warton Marsh. The Tillingham Marsh sediments were more resistant to erosion, including within the upper section. This indicates possible variability in the mechanical role of rooting structures (as also found in previous work (e.g. Feagin et al. 2009; Ford et al. 2016)), under a different marsh sedimentology.</p><p>Small-scale marsh stability is thus strongly influenced by physical sedimentology, biological root structures, hydrodynamic sequencing, and the interactions between these factors. A combination of inundation history, bulk sediment strength and belowground vegetation structure is likely to influence salt marsh lateral stability, at least at the cm to m scale. Understanding under which conditions (e.g. location, wave regime) these factors become more or less important, and how these small scale controls scale up to larger scales is crucial towards modelling and predicting future salt marsh change.</p><p>References:</p><ul><li>Feagin, R. A., Lozada-Bernard, S. M., Ravens, T. M., Möller, I., Yeager, K. M., & Baird, A. H. (2009). Does vegetation prevent wave erosion of salt marsh edges? Proceedings of the National Academy of Sciences of the United States of America, 106(25), 10109–10113. https://doi.org/10.1073/pnas.0901297106</li> <li>Ford, H., Garbutt, A., Ladd, C., Malarkey, J., & Skov, M. W. (2016). Soil stabilization linked to plant diversity and environmental context in coastal wetlands. Journal of Vegetation Science, 27(2), 259–268. https://doi.org/10.1111/jvs.12367</li> </ul>

USE OF AERIAL IMAGES IN RESEARCH OF MASS MOVEMENTS – A CASE STUDY OF THE LACHOWICE LANDSLIDE (WESTERN CARPATHIANS, BESKID MAKOWSKI MTS)

2016 ◽  
pp. 115-122 ◽  
Author(s):  
Krzysztof Karwacki
Keyword(s):  
Horizontal Displacement ◽  
Aerial Images ◽  
Rock Masses ◽  
Aerial Photos ◽  
Digital Terrain ◽  
Terrain Models ◽  
Displacement Vectors ◽  
Digital Elevation

The article presents the application of photogrammetric digital elevation models in the study of the Lachowice landslide. For this purpose, aerial photos taken in 1977, 2003, 2009 have been used. Digital terrain models (DTM) have been produced from the point cloud generated on the aerial images, using images matching. Generated models allowed calculating the volume of displaced rock masses. Zones of loss and accumulation of rock masses have also been identified. The presence of identifiable points on all images enabled the determination of the values and directions of horizontal displacement vectors.

scholarly journals Heterogeneous glacier thinning patterns over the last 40 years in Langtang Himal, Nepal

2016 ◽  
Vol 10 (5) ◽  
pp. 2075-2097 ◽  
Author(s):  
Silvan Ragettli ◽  
Tobias Bolch ◽  
Francesca Pellicciotti
Keyword(s):  
Satellite Imagery ◽  
Elevation Change ◽  
Volume Changes ◽  
Change Rate ◽  
Digital Elevation ◽  
Ensemble Mean ◽  
Glacier Front ◽  
Elevation Changes ◽  
Elevation Model ◽  
2015 Nepal Earthquake

Abstract. This study presents volume and mass changes of seven (five partially debris-covered, two debris-free) glaciers in the upper Langtang catchment in Nepal. We use a digital elevation model (DEM) from 1974 stereo Hexagon satellite data and seven DEMs derived from 2006–2015 stereo or tri-stereo satellite imagery (e.g., SPOT6/7). The availability of multiple independent DEM differences allows the identification of a robust signal and narrowing down of the uncertainty about recent volume changes. The volume changes calculated over several multiyear periods between 2006 and 2015 consistently indicate that glacier thinning has accelerated with respect to the period 1974–2006. We calculate an ensemble-mean elevation change rate of –0.45 ± 0.18 m a−1 for 2006–2015, while for the period 1974–2006 we compute a rate of −0.24 ± 0.08 m a−1. However, the behavior of glaciers in the study area is heterogeneous, and the presence or absence of debris does not seem to be a good predictor for mass balance trends. Debris-covered tongues have nonlinear thinning profiles, and we show that recent accelerations in thinning correlate with the presence of supraglacial cliffs and lakes. At stagnating glacier areas near the glacier front, however, thinning rates decreased with time or remained constant. The April 2015 Nepal earthquake triggered large avalanches in the study catchment. Analysis of two post-earthquake DEMs revealed that the avalanche deposit volumes remaining 6 months after the earthquake are negligible in comparison to 2006–2015 elevation changes. However, the deposits compensate about 40 % the mass loss of debris-covered tongues of 1 average year.

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