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 Quality Assessment and Glaciological Applications of Digital Elevation Models Derived from Space-Borne and Aerial Images over Two Tidewater Glaciers of Southern Spitsbergen

2019 ◽  
Vol 11 (9) ◽  
pp. 1121 ◽  
Author(s):  
Małgorzata Błaszczyk ◽  
Dariusz Ignatiuk ◽  
Mariusz Grabiec ◽  
Leszek Kolondra ◽  
Michał Laska ◽  
...  
Keyword(s):  
Mass Balance ◽  
Digital Elevation Models ◽  
Control Point ◽  
Aerial Photographs ◽  
Differential Gps ◽  
Tidewater Glaciers ◽  
Digital Elevation ◽  
High Resolution Satellite Images ◽  
Elevation Changes ◽  
Geodetic Mass Balance

In this study, we assess the accuracy and precision of digital elevation models (DEM) retrieved from aerial photographs taken in 2011 and from Very High Resolution satellite images (WorldView-2 and Pléiades) from the period 2012–2017. Additionally, the accuracy of the freely available Strip product of ArcticDEM was verified. We use the DEMs to characterize geometry changes over Hansbreen and Hornbreen, two tidewater glaciers in southern Spitsbergen, Svalbard. The satellite-based DEMs from WorldView-2 and Pléiades stereo pairs were processed using the Rational Function Model (RFM) without and with one ground control point. The elevation quality of the DEMs over glacierized areas was validated with in situ data: static differential GPS survey of mass balance stakes and GPS kinematic data acquired during ground penetrating radar survey. Results demonstrate the usefulness of the analyzed sources of DEMs for estimation of the total geodetic mass balance of the Svalbard glaciers. DEM accuracy is sufficient to investigate glacier surface elevation changes above 1 m. Strips from the ArcticDEM are generally precise, but some of them showed gross errors and need to be handled with caution. The surface of Hansbreen and Hornbreen has been lowering in recent years. The average annual elevation changes for Hansbreen were more negative in the period 2015–2017 (−2.4 m a−1) than in the period 2011–2015 (−1.7 m a−1). The average annual elevation changes over the studied area of Hornbreen for the period 2012–2017 amounted to −1.6 m a−1. The geodetic mass balance for Hansbreen was more negative than the climatic mass balance estimated using the mass budget method, probably due to underestimation of the ice discharge. From 2011 to 2017, Hansbreen lost on average over 1% of its volume each year. Such a high rate of relative loss illustrates how fast these glaciers are responding to climate change.

An open-source toolset for automated processing of historic spy photos: sPyMicMac

2020 ◽  
Author(s):  
Robert McNabb ◽  
Luc Girod ◽  
Christopher Nuth ◽  
Andreas Kääb
Keyword(s):  
High Resolution ◽  
Open Source ◽  
Digital Elevation Models ◽  
Automated Detection ◽  
The Arctic ◽  
Ground Control ◽  
High Mountain ◽  
Landsat 8 ◽  
Elevation Change ◽  
Digital Elevation

<p>First launched in 1971, the KH-9 “Hexagon” reconnaissance satellites were operational until 1986. In addition to the high-resolution main cameras, the satellites had a secondary camera system, the mapping camera, which acquired images at approximately 6-10m ground resolution. These images, declassified in 2002, provide an unparalleled ability to extend records of elevation change over areas of the world where older data, typically from aerial photogrammetry, are missing, unavailable, or unreliable, including High Mountain Asia and the Arctic. These images are not, however, free from challenges. Storage and film processing have introduced warping into the images, and the large film format means that images are scanned in halves which must be precisely re-aligned for photogrammetric processing.</p><p> </p><p>Building on previous efforts, we have developed an open-source toolset, based in python, that performs several of the steps necessary for processing digital elevation models (DEMs) from the raw imagery within MicMac. These include precise re-alignment based on dense keypoint detection, automated detection of the reseau field to aid in un-warping of the images, color balancing to increase contrast in low-contrast areas, and automated detection of ground control points using modern orthorectified satellite images such as Sentinel-2 and Landsat 8, and high-resolution digital elevation models such as ArcticDEM. Each of these tools interface with the MicMac photogrammetry software package that performs each of the steps necessary for DEM extraction.</p><p> </p><p>We have tested this toolset on scenes from Alaska, Iceland, and Norway. Comparison to external elevation datasets such as NASA’s Ice, Cloud and Elevation Satellite (ICESat), ArcticDEM, and national elevation products yields agreement of better than 10 m root mean square error over stable terrain, even in mountainous areas. In particular, we obtain satisfactory results in remote areas where precise ground control measurements are difficult to obtain. This toolset provides the ability to easily extend records of precise elevation change in areas where very little historic data exist. In addition, the GCP matching routine can be used to process other air photo datasets, providing a useful tool for processing older photo archives.</p>

scholarly journals Glacier elevation and mass changes over the central Karakoram region estimated from TanDEM-X and SRTM/X-SAR digital elevation models

2016 ◽  
Vol 57 (71) ◽  
pp. 273-281 ◽  
Author(s):  
Melanie Rankl ◽  
Matthias Braun
Keyword(s):  
High Resolution ◽  
Snow Cover ◽  
Digital Elevation Models ◽  
Mass Balances ◽  
Freshwater Resources ◽  
Digital Elevation ◽  
Glacier Changes ◽  
Kinematic Waves ◽  
Elevation Changes ◽  
River Communities

AbstractSnow cover and glaciers in the Karakoram region are important freshwater resources for many down-river communities as they provide water for irrigation and hydropower. A better understanding of current glacier changes is hence an important informational baseline. We present glacier elevation changes in the central Karakoram region using TanDEM-X and SRTM/X-SAR DEM differences between 2000 and 2012. We calculated elevation differences for glaciers with advancing and stable termini or surge-type glaciers separately using an inventory from a previous study. Glaciers with stable and advancing termini since the 1970s showed nearly balanced elevation changes of -0.09 ±0.12 m a-1 on average or mass budgets of -0.01 ±0.02Gt a-1 (using a density of 850 kg m-3). Our findings are in accordance with previous studies indicating stable or only slightly negative glacier mass balances during recent years in the Karakoram. The high-resolution elevation changes revealed distinct patterns of mass relocation at glacier surfaces during active surge cycles. The formation of kinematic waves at quiescent surge-type glaciers could be observed and points towards future active surge behaviour. Our study reveals the potential of the TanDEM-X mission to estimate geodetic glacier mass balances, but also points to still existing uncertainties induced by the geodetic method.

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 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.

scholarly journals Examining geodetic glacier mass balance in the eastern Pamir transition zone

2020 ◽  
Vol 66 (260) ◽  
pp. 927-937
Author(s):  
Mingyang Lv ◽  
Duncan J. Quincey ◽  
Huadong Guo ◽  
Owen King ◽  
Guang Liu ◽  
...  
Keyword(s):  
Mass Balance ◽  
Statistical Difference ◽  
Mass Gain ◽  
High Mountain ◽  
Glacier Mass Balance ◽  
Negative Mass ◽  
Glacier Surface ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Individual Scale

AbstractGlaciers in the eastern Pamir have reportedly been gaining mass during recent decades, even though glaciers in most other regions in High Mountain Asia have been in recession. Questions still remain about whether the trend is strengthening or weakening, and how far the positive balances extend into the eastern Pamir. To address these gaps, we use three different digital elevation models to reconstruct glacier surface elevation changes over two periods (2000–09 and 2000–15/16). We characterize the eastern Pamir as a zone of transition from positive to negative mass balance with the boundary lying at the northern end of Kongur Tagh, and find that glaciers situated at higher elevations are those with the most positive balances. Most (67% of 55) glaciers displayed a net mass gain since the 21st century. This led to an increasing regional geodetic glacier mass balance from −0.06 ± 0.16 m w.e. a−1 in 2000–09 to 0.06 ± 0.04 m w.e. a−1 in 2000–15/16. Surge-type glaciers, which are prevalent in the eastern Pamir, showed fluctuations in mass balance on an individual scale during and after surges, but no statistical difference compared to non-surge-type glaciers when aggregated across the region.

Occurrence and characteristics of ice-debris landforms in Poiqu basin (central Himalaya)

2020 ◽  
Author(s):  
Tobias Bolch ◽  
Philipp Rastner ◽  
Jan Bouke Pronk ◽  
Atanu Bhattacharya ◽  
Lin Liu ◽  
...  
Keyword(s):  
Surface Elevation ◽  
High Mountain ◽  
Central Himalaya ◽  
Digital Elevation ◽  
Debris Transport ◽  
Elevation Changes ◽  
Movement Field ◽  
Rock Glaciers ◽  
Southern Tibetan Plateau ◽  
Satellite Radar

<p>Rock glaciers and other ice-debris landforms (I-DLs) are an important part of the debris-transport system in high mountains and their internal ice could provide a relevant contribution to water supply especially in dry regions. Recent research has shown that I-DLs are abundant in High Mountain Asia, but knowledge about their occurrence and characteristics is still limited.</p><p>We are therefore investigating I-DLs in the Poiqu basin (~28°17´N, 85°58´E) – central Himalaya/southern Tibetan Plateau using remote sensing aided by field observations. We use very high-resolution stereo Pleiades data from the contemporary period and stereo Corona and Hexagon data from the 1970s to generate digital elevation models, applied satellite radar interferometry based on ALOS-1 PALSAR and Sentinel-1 SAR data and feature tracking using Sentinel-2 and the Pleiades data. Generated DEMs allowed us to create a hillshade to support identification, to derive their topographical parameters and to investigate surface elevation changes. I-DLs were identified and classified based on their characteristic shape, their surface structure and surface movement. Field observationssupported the identification of the landforms.</p><p>We found abundant occurrence of rock glaciers (with typical characteristics like lobate-shaped forms, ridges and furrows as well as steep fronts) but also significant movements of both former lateral moraines and debris-slopes in permafrost area. Preliminary results revealed the occurrence of more than 350 rock glaciers covering an area of about 21 km<sup>2</sup>. About 150 of them are active. The largest rock glacier has an area of 0.5 km<sup>2</sup> and three have an area of more than 0.3 km<sup>2</sup>. The rock glaciers are located between ~3715 m and ~5850 m with a mean altitude of ~5075 m a.s.l.. The mean slope of all rock glaciers is close to 17.5° (min. 6.8°, max. 37.6°). Most of the rock glaciers face towards the Northeast (19%) and West (18.5%). Surface elevation changes between the 1970s and 2018 show no significant changes but indicate slight elevation gain at the front of active rock glaciers caused by their downward movements.</p><p>Work will be continued to generate an inventory of all I-DLs in the study area including information about their activity and surface elevation changes.</p>

Multi-decadal ice-velocity and elevation changes of a monsoonal maritime glacier: Hailuogou glacier, China

2010 ◽  
Vol 56 (195) ◽  
pp. 65-74 ◽  
Author(s):  
Yong Zhang ◽  
Koji Fujita ◽  
Shiyin Liu ◽  
Qiao Liu ◽  
Xin Wang
Keyword(s):  
Thermal Emission ◽  
Surface Elevation ◽  
Aerial Photographs ◽  
Differential Gps ◽  
Glacier Surface ◽  
Ablation Area ◽  
Glacier Terminus ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Ice Velocity

AbstractDigital elevation models (DEMs) of the ablation area of Hailuogou glacier, China, produced from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data obtained in 2009, differential GPS (DGPS) data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long- and short-term glacier surface elevation change (dh/dt). The mean dh/dt of the ablation area over 43 years (1966–2009) is −1.1 ± 0.4 m a−1. Since 1989 the thinning has accelerated significantly. Ice velocities measured by DGPS at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus, ranging from 41.0 m a−1 approaching the glacier terminus to a maximum of 205.0 m a−1 at the base of an icefall. Our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades. Changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics, which are driven by different factors for different regions and periods.

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