scholarly journals Interferometric swath processing of Cryosat data for glacial ice topography

2013 ◽  
Vol 7 (6) ◽  
pp. 1857-1867 ◽  
Author(s):  
L. Gray ◽  
D. Burgess ◽  
L. Copland ◽  
R. Cullen ◽  
N. Galin ◽  
...  
Keyword(s):  
European Space Agency ◽  
Main Beam ◽  
Synthetic Aperture Radar Interferometry ◽  
Ice Cap ◽  
Space Agency ◽  
Digital Elevation ◽  
Interferometric Phase ◽  
Elevation Data ◽  
Devon Ice Cap ◽  
Cross Track

Abstract. We have derived digital elevation models (DEMs) over the western part of the Devon Ice Cap in Nunavut, Canada, using "swath processing" of interferometric data collected by Cryosat between February 2011 and January 2012. With the standard ESA (European Space Agency) SARIn (synthetic aperture radar interferometry) level 2 (L2) data product, the interferometric mode is used to map the cross-track position and elevation of the "point-of-closest-approach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of time-delayed footprints beyond the POCA. We show that there is a range of average cross-track slopes (~ 0.5 to ~ 2°) for which the returns will be dominated by those beneath the satellite in the main beam of the antenna so that the resulting interferometric phase allows mapping of heights in the delayed range window beyond the POCA. In this way a swath of elevation data is mapped, allowing the creation of DEMs from a sequence of L1b SARIn Cryosat data takes. Comparison of the Devon results with airborne scanning laser data showed a mean difference of order 1 m with a standard deviation of about 1 m. The limitations of swath processing, which generates almost 2 orders of magnitude more data than traditional radar altimetry, are explored through simulation, and the strengths and weaknesses of the technique are discussed.

scholarly journals Interferometric swath processing of Cryosat-2 data for glacial ice topography

2013 ◽  
Vol 7 (3) ◽  
pp. 3133-3162 ◽  
Author(s):  
L. Gray ◽  
D. Burgess ◽  
L. Copland ◽  
R. Cullen ◽  
N. Galin ◽  
...  
Keyword(s):  
Digital Elevation Models ◽  
Main Beam ◽  
Glacial Ice ◽  
Ice Cap ◽  
Digital Elevation ◽  
Interferometric Phase ◽  
Elevation Data ◽  
Devon Ice Cap ◽  
Cross Track ◽  
Level 2

Abstract. We have derived Digital Elevation Models (DEMs) over the western part of the Devon Ice Cap in Nunavut Canada using "swath processing" of interferometric data collected by Cryosat 2 between February 2011 and January 2012. In the standard ESA "SARIn" level 2 (L2) data product the interferometric mode is used to map the cross-track position and elevation of the "point-of-closest-approach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of time delayed footprints beyond the POCA. We show that there is a range of average cross-track slopes (~0.5° to ~2°) for which the returns will be dominated by those beneath the satellite in the main beam of the antenna and that the resulting interferometric phase allows mapping of heights in the delayed range window beyond the POCA. In this way a swath of elevation data is mapped allowing the creation of Digital Elevation Models (DEMs) from a sequence of L1b SARIn Cryosat-2 data takes. Comparison of the Devon results with airborne scanning laser data showed a mean difference of order a meter with a standard deviation < 1 m. The limitations of swath processing, which generates almost 2 orders of magnitude more data than traditional radar altimetry, are explored through simulation, and the strengths and weaknesses of the technique are discussed.

scholarly journals Interferometric discrimination of cross-track bed clutter in ice-penetrating radar sounding data

2020 ◽  
Vol 61 (81) ◽  
pp. 68-73 ◽  
Author(s):  
Kirk M. Scanlan ◽  
Anja Rutishauser ◽  
Duncan A. Young ◽  
Donald D. Blankenship
Keyword(s):  
Center Frequency ◽  
Adjacent Area ◽  
Bed Topography ◽  
Ice Cap ◽  
Digital Elevation ◽  
Interferometric Phase ◽  
Devon Ice Cap ◽  
Track Surface ◽  
Cross Track ◽  
Climate Studies

AbstractThe interpretations of relevant interfaces (i.e. the surface and bed) in radar sounding datasets over glaciers and ice sheets are primary boundary conditions in a variety of climate studies and particularly subglacial water routing models. It is therefore necessary to ensure these interpretations are consistent and not affected by cross-track clutter. For the surface interface, interferometry and a family of methods relying on digital elevation models have been used to successfully discriminate cross-track surface clutter. Here we present how interferometry can be applied to the problem of basal clutter from cross-track bed topography. Our approach is based on a comparison of the differential phases of ambiguous reflectors that may represent bed clutter and the differential phase of a reflector in an adjacent area that appears unaffected by basal clutter. The reflector yielding the smallest interferometric phase difference relative to the unambiguous bed reflector is considered to represent its consistent continuation. We successfully demonstrate our approach using 60 MHz center frequency MARFA data collected over Devon Ice Cap in the Canadian Arctic. Finally, we investigate the effects of clutter-affected and interferometry-corrected bed interpretations on ice layer thickness estimates, basal hydraulic head gradients and the potential extent of inferred subglacial water bodies.

scholarly journals Using airborne Ku-band altimeter waveforms to investigate winter accumulation and glacier facies on Austfonna, Svalbard

2013 ◽  
Vol 59 (217) ◽  
pp. 893-899 ◽  
Author(s):  
Robert L. Hawley ◽  
Ola Brandt ◽  
Thorben Dunse ◽  
Jon Ove Hagen ◽  
Veit Helm ◽  
...  
Keyword(s):  
Snow Depth ◽  
European Space Agency ◽  
Synthetic Aperture Radar Image ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Ice Caps ◽  
Ice Cap ◽  
Space Agency ◽  
Wet Snow ◽  
Airborne Sar

AbstractWinter balance is an important metric for assessing the change on glaciers and ice caps, yet measuring it using ground-based techniques can be challenging. We use the European Space Agency prototype Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) to extract snow depths from the received altimeter waveforms over Austfonna ice cap, Svalbard. Additionally, we attempt to distinguish the long-term firn area from other glacier facies. We validate our results using snow depth and glacier facies characterizations determined from ground-based radar profiles, snow pits and a multi-look satellite synthetic aperture radar image. We show that the depth of the winter snowpack can be extracted from the altimeter data over most of the accumulation zone, comprising wet snow zone and a superimposed ice zone. The method struggles at lower elevations where internal reflections within the winter snowpack are strong and the winter snow depth is less than ∼1 m. We use the abruptness of the reflection from the last summer surface (LSS) to attempt to distinguish glacier facies. While there is a general correlation between LSS abruptness and glacier facies, we do not find a relationship that warrants a distinct classification based on ASIRAS waveforms alone.

scholarly journals Improved processing and calibration of the interferometric mode of the CryoSat radar altimeter allows height measurements of supraglacial lakes in west Greenland

2016 ◽  
Author(s):  
Laurence Gray ◽  
David Burgess ◽  
Luke Copland ◽  
Thorben Dunse ◽  
Kirsty Langley ◽  
...  
Keyword(s):  
Normal Incidence ◽  
Ablation Zone ◽  
Radar Altimeter ◽  
Waveform Data ◽  
West Greenland ◽  
Ice Cap ◽  
Supraglacial Lakes ◽  
Ideal Situation ◽  
Digital Elevation ◽  
Devon Ice Cap

Abstract. We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration-validation sites on Devon Ice Cap and West Greenland. Comparisons are included for both the heights derived from the first return (the "point-of-closest-approach" or POCA) as well as heights derived from delayed waveform returns ("swath" processing). While swath processed heights are normally less accurate than edited POCA heights, of order 1–5 m instead of order 1–2 m, the increased coverage possible with swath data complements the POCA data and provides useful information for both system calibration and improving digital elevation models (DEMs). We show that the pre-launch interferometric baseline coupled with an additional roll correction (~ 0.0075°), or equivalent phase correction (~ 0.0435 radians), provides an improved calibration of the interferometric SARIn mode. We extend the potential use of SARIn data by showing the influence of surface conditions, especially melt, on the return waveforms, and that it is possible to detect and measure the height of summer supraglacial lakes in West Greenland. A supraglacial lake can provide a strong radar target in the waveform, stronger than the initial POCA return, if viewed at near normal incidence. This provides an ideal situation for swath processing and we demonstrate height accuracies of ~ 0.5 m for two lake sites, one in the accumulation zone and one in the ablation zone, which were measured every year from 2010 or 2011 to 2016. Each year the lake in the ablation zone was viewed in June by ascending passes and then 5.5 days later by descending passes which allows an approximate estimate of the filling rate. The results suggest that CryoSat waveform data and measurements of supraglacial lake height change could complement the use of optical satellite and be helpful as proxy indicators for surface melt around Greenland.

scholarly journals The Global Water Body Layer from TanDEM-X Interferometric SAR Data

2021 ◽  
Vol 13 (24) ◽  
pp. 5069
Author(s):  
Jose-Luis Bueso-Bello ◽  
Michele Martone ◽  
Carolina González ◽  
Francescopaolo Sica ◽  
Paolo Valdo ◽  
...  
Keyword(s):  
Water Body ◽  
European Space Agency ◽  
Water Layer ◽  
Global Scale ◽  
Data Set ◽  
Primary Input ◽  
Water Detection ◽  
Space Agency ◽  
Digital Elevation ◽  
Global Water

The interferometric synthetic aperture radar (InSAR) data set, acquired by the TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) mission (TDM), represents a unique data source to derive geo-information products at a global scale. The complete Earth’s landmasses have been surveyed at least twice during the mission bistatic operation, which started at the end of 2010. Examples of the delivered global products are the TanDEM-X digital elevation model (DEM) (at a final independent posting of 12 m × 12 m) or the TanDEM-X global Forest/Non-Forest (FNF) map. The need for a reliable water product from TanDEM-X data was dictated by the limited accuracy and difficulty of use of the TDX Water Indication Mask (WAM), delivered as by-product of the global DEM, which jeopardizes its use for scientific applications, as well. Similarly as it has been done for the generation of the FNF map; in this work, we utilize the global data set of TanDEM-X quicklook images at 50 m × 50 m resolution, acquired between 2011 and 2016, to derive a new global water body layer (WBL), covering a range from −60∘ to +90∘ latitudes. The bistatic interferometric coherence is used as the primary input feature for performing water detection. We classify water surfaces in single TanDEM-X images, by considering the system’s geometric configuration and exploiting a watershed-based segmentation algorithm. Subsequently, single overlapping acquisitions are mosaicked together in a two-step logically weighting process to derive the global TDM WBL product, which comprises a binary averaged water/non-water layer as well as a permanent/temporary water indication layer. The accuracy of the new TDM WBL has been assessed over Europe, through a comparison with the Copernicus water and wetness layer, provided by the European Space Agency (ESA), at a 20 m × 20 m resolution. The F-score ranges from 83%, when considering all geocells (of 1∘ latitudes × 1∘ longitudes) over Europe, up to 93%, when considering only the geocells with a water content higher than 1%. At global scale, the quality of the product has been evaluated, by intercomparison, with other existing global water maps, resulting in an overall agreement that often exceeds 85% (F-score) when the content in the geocell is higher than 1%. The global TDM WBL presented in this study will be made available to the scientific community for free download and usage.

scholarly journals TWO-FREQUENCY CROSS-SLOT ANTENNA WITH RESONANT COLD ELECTRON BOLOMETERS FOR APPLICATION IN CORE SPACE MISSION

2017 ◽  
Vol 8 (2) ◽  
pp. 101-107
Author(s):  
L. S. Kuzmin ◽  
A. V. Chiginev
Keyword(s):  
Metal Layer ◽  
European Space Agency ◽  
Dielectric Substrate ◽  
Antenna System ◽  
Slot Antenna ◽  
Main Beam ◽  
Cold Electron ◽  
Dual Frequency ◽  
Actual Problem ◽  
Space Agency

Measurements of the CMB properties is an actual problem of modern astronomy. The aim of the present paper is the numerical modeling of the two-frequency planar cross-slot antenna designed for operation in the receiving system of the orbital telescope Cosmic Origins Explorer (COrE), developed by the European Space Agency to measure the CMB.The proposed antenna is a planar metal layer on the dielectric substrate, and comprising a set of four slots intersecting each other at right angles. The composition also includes a set of microstrip lines for transmitting a signal from the resonant slots to cold-electron bolometers, and a lens for forming the main beam of the radiation diagram. Calculation of the antenna system is made by electrodynamic modeling software package CST Microwave Studio. As a result of the modeling, the radiation diagram of the antenna in two frequency channels as well as its frequency characteristics are obtained.The calculation gives the following characteristics of the receiving system on the basis of cross-slot antenna: width of the main beam of the radiation diagram – 24.3° and 19.5°, the ellipticity of the beam – 4.2 % and 0.3 %, the bandwidth – 14.9 GHz and 19.0 GHz, polarization resolution – 23.4 dB and 29.6 dB, where the former value refers to the 75 GHz channel, and the latter refers to 105 GHz channel.It is proposed to use a cross-slot antenna in dual-frequency mode together with resonant cold-electron bolometers to work in the receiving system of the orbital telescope COrE. Comparison of the calculated antenna characteristics with the requirements set by the European Space Agency, have shown the possibility of using this type of antenna as part COrE mission.

scholarly journals Estimation of Velocity of the Polar Record Glacier, Antarctica Using Synthetic Aperture Radar (SAR)

Proceedings ◽  
2018 ◽  
Vol 2 (7) ◽  
pp. 332
Author(s):  
Prashant H. Pandit ◽  
Shridhar D. Jawak ◽  
Alvarinho J. Luis
Keyword(s):  
Synthetic Aperture Radar ◽  
European Space Agency ◽  
Velocity Estimation ◽  
Synthetic Aperture ◽  
Persistent Scatterer Interferometry ◽  
Synthetic Aperture Radar Interferometry ◽  
Space Agency ◽  
Persistent Scatterer ◽  
Glacier Velocity ◽  
Aperture Radar

The ice flow velocity is a critical variable in understanding the glacier dynamics. The Synthetic Aperture Radar Interferometry (InSAR) is a robust technique to monitor Earth’s surface mainly to measure its topography and deformation. The phase information from two or more interferogram further helps to extract information about the height and displacement of the surface. We used this technique to derive glacier velocity for Polar Record Glacier (PRG), East Antarctica, using Sentinel-1 Single Look Complex images that were captured in Interferometric Wide mode. For velocity estimation, Persistent Scatterer interferometry (PS-InSAR) method was applied, which uses the time coherent of permanent pixel of master images and correlates to the same pixel of the slave image to get displacement by tracking the intensity of those pixels. C-band sensor of European Space Agency, Sentinel-1A, and 1B data were used in this study. Estimated average velocity of the PRG is found to be approximately ≈400 ma−1, which varied from ≈100 to ≈700 ma−1. We also found that PRG moves at ≈700 and 200 ma−1 in the lower part and the upper inland area, respectively.

scholarly journals Assessing Urban Landslide Dynamics through Multi-Temporal InSAR Techniques and Slope Numerical Modeling

2021 ◽  
Vol 13 (19) ◽  
pp. 3862
Author(s):  
Nicușor Necula ◽  
Mihai Niculiță ◽  
Simone Fiaschi ◽  
Rinaldo Genevois ◽  
Paolo Riccardi ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
European Space Agency ◽  
Landslide Risk ◽  
Sar Images ◽  
Conditioning Factors ◽  
Environmental Conditioning ◽  
Synthetic Aperture Radar Interferometry ◽  
Space Agency ◽  
Multi Temporal ◽  
Landslide Dynamics

Landslides threaten more than before the urbanized areas and are a worldwide growing problem for the already affected communities and the local authorities committed to landslide risk management and mitigation. For this reason, it is essential to analyze landslide dynamics and environmental conditioning factors. Various techniques and instruments exist for landslide investigation and monitoring. Out of these, Multi-temporal Synthetic Aperture Radar Interferometry (MT-InSAR) techniques have been widely used in the last decades. Their capabilities are enhanced by the availability of the active Sentinel-1 mission, whose 6-day revisiting time enables near real-time monitoring of landslides. Interferometric results, coupled with ground measurements or other approaches such as numerical modeling, significantly improve the knowledge of the investigated surface processes. In this work, we processed the C-band SAR images of the available European Space Agency (ESA) satellite missions, using MT-InSAR methods to identify the surface deformations related to landslides affecting the Iași Municipality (Eastern Romania). The results (i.e., velocity maps) point out the most active landslides with velocities of up to 20 mm/year measured along the satellite Line of Sight (LOS). Following, we focused on the most problematic landslide that affects the Țicău neighborhood and is well-known for its significant implications that it had. To better understand its behavior and the sensitivity of the displacements to the environmental factors (i.e., rainfall), we carried out 2D numerical modeling using a finite difference code. The simulated displacement field is consistent with the InSAR displacements and reveals the most active sectors of the landslide and insights about its mechanism.

scholarly journals A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland

2017 ◽  
Vol 11 (3) ◽  
pp. 1041-1058 ◽  
Author(s):  
Laurence Gray ◽  
David Burgess ◽  
Luke Copland ◽  
Thorben Dunse ◽  
Kirsty Langley ◽  
...  
Keyword(s):  
Normal Incidence ◽  
Ablation Zone ◽  
Radar Altimeter ◽  
Waveform Data ◽  
Ice Cap ◽  
Supraglacial Lakes ◽  
Ideal Situation ◽  
Digital Elevation ◽  
Devon Ice Cap ◽  
Height Change

Abstract. We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration–validation sites on Devon Ice Cap and western Greenland. Comparisons are included for both the heights derived from the first return (the point-of-closest-approach or POCA) and heights derived from delayed waveform returns (swath processing). While swath-processed heights are normally less precise than edited POCA heights, e.g. standard deviations of  ∼  3 and  ∼  1.5 m respectively for the western Greenland site, the increased coverage possible with swath data complements the POCA data and provides useful information for both system calibration and improving digital elevation models (DEMs). We show that the pre-launch interferometric baseline coupled with an additional roll correction ( ∼  0.0075° ± 0.0025°), or equivalent phase correction ( ∼  0.0435 ± 0.0145 radians), provides an improved calibration of the interferometric SARIn mode. We extend the potential use of SARIn data by showing the influence of surface conditions, especially melt, on the return waveforms and that it is possible to detect and measure the height of summer supraglacial lakes in western Greenland. A supraglacial lake can provide a strong radar target in the waveform, stronger than the initial POCA return, if viewed at near-normal incidence. This provides an ideal situation for swath processing and we demonstrate a height precision of  ∼  0.5 m for two lake sites, one in the accumulation zone and one in the ablation zone, which were measured every year from 2010 or 2011 to 2016. Each year the lake in the ablation zone was viewed in June by ascending passes and then 5.5 days later by descending passes, which allows an approximate estimate of the filling rate. The results suggest that CryoSat waveform data and measurements of supraglacial lake height change could complement the use of optical satellite imagery and be helpful as proxy indicators for surface melt around Greenland.

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