scholarly journals Accurate Determination of Glacier Surface Velocity Fields with a DEM-Assisted Pixel-Tracking Technique from SAR Imagery

2015 ◽  
Vol 7 (8) ◽  
pp. 10898-10916 ◽  
Author(s):  
Shiyong Yan ◽  
Guang Liu ◽  
Yunjia Wang ◽  
Zhixing Ruan
Keyword(s):  
Accurate Determination ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Glacier Surface ◽  
Tracking Technique ◽  
Sar Imagery

scholarly journals AUTOMATIC MAPPING OF GLACIER BASED ON SAR IMAGERY BY BENEFITS OF FREELY OPTICAL AND THERMAL DATA

2015 ◽  
Vol XL-3/W2 ◽  
pp. 47-51
Author(s):  
L. Fang ◽  
L. Hoegner ◽  
U. Stilla
Keyword(s):  
Land Surface ◽  
Low Resolution ◽  
Glacier Surface ◽  
Thermal Data ◽  
Automatic Mapping ◽  
Resources Evaluation ◽  
Sar Imagery ◽  
Normalized Difference Snow Index ◽  
Occurrence Matrix

For many research applications like water resources evaluation, determination of glacier specific changes, and for calculation of the past and future contribution of glaciers to sea-level change, parameters about the size and spatial distribution of glaciers is crucial. In this paper, an automatic method for determination of glacier surface area using single track high resolution TerraSAR-X imagery by benefits of low resolution optical and thermal data is presented. Based on the normalized difference snow index (NDSI) and land surface temperature (LST) map generated from optical and thermal data combined with a surface slope data, a low resolution binary mask was derived used for the supervised classification of glacier using SAR imagery. Then, a set of suitable features is derived from the SAR intensity image, such as the texture information generated based on the gray level co-occurrence matrix (GLCM), and the intensity values. With these features, the glacier surface is discriminated from the background by Random Forests (RF) method.

scholarly journals COPERNICUS BIG DATA AND GOOGLE EARTH ENGINE FOR GLACIER SURFACE VELOCITY FIELD MONITORING: FEASIBILITY DEMONSTRATION ON SAN RAFAEL AND SAN QUINTIN GLACIERS

2018 ◽  
Vol XLII-3 ◽  
pp. 289-294 ◽  
Author(s):  
M. Di Tullio ◽  
F. Nocchi ◽  
A. Camplani ◽  
N. Emanuelli ◽  
A. Nascetti ◽  
...  
Keyword(s):  
Time Series ◽  
Big Data ◽  
Velocity Field ◽  
Field Measurements ◽  
Google Earth ◽  
Surface Velocity ◽  
Glacier Surface ◽  
Google Earth Engine ◽  
Sar Imagery ◽  
San Rafael

The glaciers are a natural global resource and one of the principal climate change indicator at global and local scale, being influenced by temperature and snow precipitation changes. Among the parameters used for glacier monitoring, the surface velocity is a key element, since it is connected to glaciers changes (mass balance, hydro balance, glaciers stability, landscape erosion). The leading idea of this work is to continuously retrieve glaciers surface velocity using free ESA Sentinel-1 SAR imagery and exploiting the potentialities of the Google Earth Engine (GEE) platform. GEE has been recently released by Google as a platform for petabyte-scale scientific analysis and visualization of geospatial datasets. The algorithm of SAR off-set tracking developed at the Geodesy and Geomatics Division of the University of Rome La Sapienza has been integrated in a cloud based platform that automatically processes large stacks of Sentinel-1 data to retrieve glacier surface velocity field time series. We processed about 600 Sentinel-1 image pairs to obtain a continuous time series of velocity field measurements over 3 years from January 2015 to January 2018 for two wide glaciers located in the Northern Patagonian Ice Field (NPIF), the San Rafael and the San Quintin glaciers. Several results related to these relevant glaciers also validated with respect already available and renown software (i.e. ESA SNAP, CIAS) and with respect optical sensor measurements (i.e. LANDSAT8), highlight the potential of the Big Data analysis to automatically monitor glacier surface velocity fields at global scale, exploiting the synergy between GEE and Sentinel-1 imagery.

scholarly journals Global time series and temporal mosaics of glacier surface velocities, derived from Sentinel-1 data

2021 ◽  
Author(s):  
Peter Friedl ◽  
Thorsten Seehaus ◽  
Matthias Braun
Keyword(s):  
Time Series ◽  
Speckle Tracking ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Synthetic Aperture ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Data Set ◽  
Time Series Analyses ◽  
Very High

Abstract. Consistent and continuous data on glacier surface velocity are important inputs to time series analyses, numerical ice dynamic modelling and glacier mass flux computations. Since 2014, repeat-pass Synthetic Aperture Radar (SAR) data is acquired by the Sentinel-1 satellite constellation as part of ESA’s (European Space Agency) Copernicus program. It enables global, near real time-like and fully automatic processing of glacier surface velocity fields at up to 6-day temporal resolution, independent of weather conditions, season and daylight. We present a new near global data set of glacier surface velocities that comprises continuously updated scene-pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution. The velocity information is derived from archived and new Sentinel-1 SAR acquisitions by applying feature and speckle tracking. The data set covers 12 major glaciated regions outside the polar ice sheets and is generated in an HPC (High Performance Computing) environment at the University of Erlangen-Nuremberg. The velocity products are freely accessible via an interactive web portal that provides capabilities for download and simple online analyses: http://retreat.geographie.uni-erlangen.de. In this paper we give information on the data processing and how to access the data. For the example region of Svalbard, we demonstrate the potential of our products for velocity time series analyses at very high temporal resolution and assess the quality of our velocity products by comparing them to those generated from very high resolution TerraSAR-X SAR (Synthetic Aperture Radar) and Landsat-8 optical (ITS_LIVE, GoLIVE) data. We find that Landsat-8 and Sentinel-1 annual velocity mosaics are in an overall good agreement, but speckle tracking on Sentinel-1 6-day repeat acquisitions derives more reliable velocity measurements over featureless and slow moving areas than the optical data. Additionally, uncertainties of 12-day repeat Sentinel-1 mid-glacier scene-pair velocities are less than half (< 0.08 m d−1) of the uncertainties derived for 16-day repeat Landsat-8 data (0.17–0.18 m d−1).

scholarly journals EXPLOITING SENTINEL-1 AMPLITUDE DATA FOR GLACIER SURFACE VELOCITY FIELD MEASUREMENTS: FEASIBILITY DEMONSTRATION ON BALTORO GLACIER

2016 ◽  
Vol XLI-B7 ◽  
pp. 783-788 ◽  
Author(s):  
A. Nascetti ◽  
F. Nocchi ◽  
A. Camplani ◽  
C. Di Rico ◽  
M. Crespi
Keyword(s):  
Velocity Field ◽  
Template Matching ◽  
High Amplitude ◽  
Surface Velocity ◽  
Seasonal Effects ◽  
Free Access ◽  
Mountain Range ◽  
Glacier Surface ◽  
Amplitude Data ◽  
Sar Imagery

The leading idea of this work is to continuously retrieve glaciers surface velocity through SAR imagery, in particular using the amplitude data from the new ESA satellite sensor Sentinel-1 imagery. These imagery key aspects are the free access policy, the very short revisit time (down to 6 days with the launch of the Sentinel-1B satellite) and the high amplitude resolution (up to 5 m). In order to verify the reliability of the proposed approach, a first experiment has been performed using Sentinel-1 imagery acquired over the Karakoram mountain range (North Pakistan) and Baltoro and other three glaciers have been investigated. During this study, a stack of 11 images acquired in the period from October 2014 to September 2015 has been used in order to investigate the potentialities of the Sentinel-1 SAR sensor to retrieve the glacier surface velocity every month. The aim of this test was to measure the glacier surface velocity between each subsequent pair, in order to produce a time series of the surface velocity fields along the investigated period. The necessary coregistration procedure between the images has been performed and subsequently the glaciers areas have been sampled using a regular grid with a 250 &times; 250 meters posting. Finally the surface velocity field has been estimated, for each image pair, using a template matching procedure, and an outlier filtering procedure based on the signal to noise ratio values has been applied, in order to exclude from the analysis unreliable points. The achieved velocity values range from 10 to 25 meters/month and they are coherent to those obtained in previous studies carried out on the same glaciers and the results highlight that it is possible to have a continuous update of the glacier surface velocity field through free Sentinel-1 imagery, that could be very useful to investigate the seasonal effects on the glaciers fluid-dynamics.

scholarly journals Early melt season velocity fields of Langjökull and Hofsjökull, central Iceland

2015 ◽  
Vol 61 (226) ◽  
pp. 253-266 ◽  
Author(s):  
Brent Minchew ◽  
Mark Simons ◽  
Scott Hensley ◽  
Helgi Björnsson ◽  
Finnur Pálsson
Keyword(s):  
Synthetic Aperture Radar ◽  
Viscous Flow ◽  
Flow Model ◽  
Vertical Component ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Synthetic Aperture ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Aperture Radar

AbstractWe infer the horizontal velocity fields of the ice caps Langjökull and Hofsjökull, central Iceland, using repeat-pass interferometric synthetic aperture radar (InSAR). NASA’s uninhabited aerial vehicle synthetic aperture radar (UAVSAR) acquired airborne InSAR data from multiple vantage points during the early melt season in June 2012. We develop a Bayesian approach for inferring three-dimensional velocity fields from multiple InSAR acquisitions. The horizontal components generally agree with available GPS measurements wherever ice motion is well constrained by InSAR observations. We provide evidence that changes in volumetric moisture content near the glacier surface induce phase offsets that obfuscate the vertical component of the surface velocity fields, an effect that could manifest itself on any glacier that experiences surface melt. Spatial patterns in the InSAR-derived horizontal speeds are broadly consistent with the results of a simple viscous flow model, and the directionality of the InSAR-derived horizontal flow field is nearly everywhere consistent with the ice surface gradient. Significant differences between the InSAR-derived horizontal speed and the speed predicted by the viscous flow model suggest that basal slip accounts for more than half the observed outlet glacier flow.

RETREAT: A new freely available data set of  Sentinel-1 glacier velocities in regions outside the polar ice sheets

2021 ◽  
Author(s):  
Peter Friedl ◽  
Thorsten Seehaus ◽  
Matthias Braun
Keyword(s):  
Ice Sheets ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Synthetic Aperture ◽  
Polar Ice ◽  
Glacier Surface ◽  
Data Set ◽  
Polar Ice Sheets ◽  
Time Series Analyses ◽  
Very High

&lt;p&gt;Climate induced glacier change has important implications for global sea level rise, freshwater availability and geomorphologic hazards. Changes in ice dynamics and mass flow can globally be observed by long- and short-term changes in ice surface velocity. Consistent and continuous data on glacier surface velocity are important inputs to time series analyses, numerical ice dynamic modelling and glacier mass balance calculations. Therefore, glacier surface velocities have been identified as an Essential Climate Variable (ECV) that should be monitored on a regular and global scale. Since 2014, repeat-pass Synthetic Aperture Radar (SAR) data, acquired by the Sentinel-1 constellation as part of ESA&amp;#8217;s (European Space Agency) Copernicus program, enable global, near real time-like and fully automatic processing of glacier velocity fields at up to 6-day temporal resolution, independent of weather conditions, season and daylight.&lt;/p&gt;&lt;p&gt;We present a new near-global data set of Sentinel-1 glacier velocities that comprises continuously updated image pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution, derived from applying intensity feature tracking on both archived and new acquisitions. The data set covers all major glaciated regions outside the polar ice sheets and is generated in an HPC (High Performance Computing) environment at the University of Erlangen-Nuremberg. By the beginning of January 2021, we processed more than 110.000 Sentinel-1 scenes, amounting to roughly 450 TB of data. The velocity products are freely accessible via an interactive web portal (http://retreat.geographie.uni-erlangen.de) that provides capabilities for download and simple online analyses. We give information on the procedures of data generation, as well as on how to access the data and demonstrate the capabilities of our products for velocity time series analyses at very high temporal resolution. We compare our data to velocity products generated from very high resolution TerraSAR-X SAR (Synthetic Aperture Radar) and Landsat-8 optical (ITS_LIVE, GoLIVE) data. For this comparison we selected Svalbard as an example region, as it includes glaciers of a broad variety of sizes, different velocitiy magnitudes and seasonal velocity patterns, as well as very fast flowing surging glaciers and almost featureless ice caps.&lt;/p&gt;

scholarly journals Global time series and temporal mosaics of glacier surface velocities derived from Sentinel-1 data

2021 ◽  
Vol 13 (10) ◽  
pp. 4653-4675
Author(s):  
Peter Friedl ◽  
Thorsten Seehaus ◽  
Matthias Braun
Keyword(s):  
Time Series ◽  
Temporal Resolution ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Optical Data ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Data Set ◽  
Time Series Analyses ◽  
Very High

Abstract. Consistent and continuous data on glacier surface velocity are important inputs to time series analyses, numerical ice dynamic modeling and glacier mass flux computations. Since 2014, repeat-pass synthetic aperture radar (SAR) data have been acquired by the Sentinel-1 satellite constellation as part of the Copernicus program of the EU (European Union) and ESA (European Space Agency). It enables global, near-real-time-like and fully automatic processing of glacier surface velocity fields at up to 6 d temporal resolution, independent of weather conditions, season and daylight. We present a new global data set of glacier surface velocities that comprises continuously updated scene-pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution. The velocity information is derived from archived and new Sentinel-1 SAR acquisitions by applying a well-established intensity offset tracking technique. The data set covers 12 major glacierized regions outside the polar ice sheets and is generated in an HPC (high-performance computing) environment at the University of Erlangen-Nuremberg. The velocity products are freely accessible via an interactive web portal that provides capabilities for download and simple online analyses: http://retreat.geographie.uni-erlangen.de (last access: 6 October 2021). In this paper, we give information on the data processing and how to access the data. For the example region of Svalbard, we demonstrate the potential of our products for velocity time series analyses at very high temporal resolution and assess the quality of our velocity products by comparing them to those generated from very high-resolution TerraSAR-X SAR and Landsat-8 optical (ITS_LIVE, GoLIVE) data. The subset of Sentinel-1 velocities for Svalbard analyzed in this paper is accessible via the GFZ Potsdam Data Services under the DOI https://doi.org/10.5880/fidgeo.2021.016 (Friedl et al., 2021). We find that Landsat-8 and Sentinel-1 annual velocity mosaics are in an overall good agreement, but speckle tracking on Sentinel-1 6 d repeat acquisitions derives more reliable velocity measurements over featureless and slow-moving areas than the optical data. Additionally, uncertainties of 12 d repeat Sentinel-1 mid-glacier scene-pair velocities have less than half (< 0.08 m d−1) of the uncertainties derived for 16 d repeat Landsat-8 data (0.17–0.18 m d−1).

scholarly journals Photogrammetric determination of spatio-temporal velocity fields at Glaciar San Rafael in the Northern Patagonian Icefield

2010 ◽  
Vol 4 (4) ◽  
pp. 2415-2432 ◽  
Author(s):  
H.-G. Maas ◽  
G. Casassa ◽  
D. Schneider ◽  
E. Schwalbe ◽  
A. Wendt
Keyword(s):  
Digital Camera ◽  
Image Sequences ◽  
Velocity Fields ◽  
Austral Spring ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Joint Project ◽  
Spatio Temporal ◽  
San Rafael

Abstract. Glaciar San Rafael in the Northern Patagonian Icefield, with a length of 46 km and an ice area of 722 km2, is the lowest latitude tidewater outlet glacier in the world and one of the fastest and most productive glaciers in southern South America in terms of iceberg flux. In a joint project of the TU Dresden and CECS, spatio-temporal velocity fields in the region of the glacier front were determined in a campaign in austral spring of 2009. Monoscopic terrestrial image sequences were recorded with an intervallometer mode high resolution digital camera over several days. In these image sequences, a large number of glacier surface points were tracked by subpixel accuracy feature tracking techniques. Scaling and georeferencing of the trajectories obtained from image space tracking was performed via a multi-station GPS-supported photogrammetric network. The technique allows for tracking hundreds of glacier surface points at a measurement accuracy in the order of one decimeter and an almost arbitrarily high temporary resolution. The results show velocities of up to 16 m per day. No significant tidal signals could be observed. Our velocities are in agreement with earlier measurements from theodolite and satellite interferometry performed in 1986–1994, suggesting that the current thinning of 3.5 m/y at the front is not due to dynamic thinning but rather by enhanced melting.

scholarly journals Modified four-pass differential SAR interferometry for estimating mountain glacier surface velocity fields

2015 ◽  
Vol 7 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Guang Liu ◽  
Huadong Guo ◽  
Huanyin Yue ◽  
Zbigniew Perski ◽  
Shiyong Yan ◽  
...  
Keyword(s):  
Velocity Fields ◽  
Sar Interferometry ◽  
Surface Velocity ◽  
Glacier Surface ◽  
Mountain Glacier ◽  
Differential Sar Interferometry
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