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 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 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.

An evaluation of LIDAR- and IFSAR-derived digital elevation models in leaf-on conditions with USGS Level 1 and Level 2 DEMs

2003 ◽  
Vol 84 (2) ◽  
pp. 295-308 ◽  
Author(s):  
Michael E Hodgson ◽  
John R Jensen ◽  
Laura Schmidt ◽  
Steve Schill ◽  
Bruce Davis
Keyword(s):  
Digital Elevation Models ◽  
Digital Elevation ◽  
Level 1 ◽  
Level 2

scholarly journals COMPARATIVE ANALYSIS FOR METHODS OF BUILDING DIGITAL ELEVATION MODELS FROM TOPOGRAPHIC MAPS USING GEOINFORMATION TECHNOLOGIES

2021 ◽  
Vol 47 (4) ◽  
pp. 191-199
Author(s):  
Vadim Belenok ◽  
Yuriy Velikodsky ◽  
Oleksandr Nikolaienko ◽  
Nataliia Rul ◽  
Sergiy Kryachok ◽  
...  
Keyword(s):  
Digital Elevation Models ◽  
Complex Structure ◽  
Topographic Maps ◽  
Interpolation Methods ◽  
Contour Lines ◽  
Central Russian Upland ◽  
Digital Elevation ◽  
Elevation Data ◽  
The Russian Federation ◽  
Elevation Model

The article considers the question of estimating the accuracy of interpolation methods for building digital elevation models using Soviet topographic maps. The territory of the Kursk region of the Russian Federation was used as the study area, because it is located on the Central Russian Upland and characterized by the complex structure of the vertical and horizontal dissection of the relief. Contour lines automatically obtained using a Python algorithm were used as the initial elevation data to build a digital elevation model. Digital elevation models obtained by thirteen different interpolation methods in ArcGIS and Surfer software were built and analyzed. Special attention is paid to the ANUDEM method, which allows to obtain hydrologically correct digital elevation models. Recommendations for the use of one or another method of interpolation are given. The results can be useful for professionals who use topographic maps in their work and deals with the design using digital elevation models.

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 COMPARING ICESAT/GLAS BASED ELEVATION HEIGHTS WITH PHOTOGRAMMETRIC TERRAIN HEIGHTS FROM UAV-IMAGERY ON THE EAST TIBETAN PLATEAU

2015 ◽  
Vol XL-3/W3 ◽  
pp. 385-390 ◽  
Author(s):  
F. Enßle ◽  
A. Fritz ◽  
B. Koch
Keyword(s):  
Tibetan Plateau ◽  
Digital Elevation Models ◽  
Shuttle Radar Topography Mission ◽  
Aerial Images ◽  
Laser Altimeter ◽  
Ice Cloud ◽  
Digital Elevation ◽  
Surface Models ◽  
Elevation Data ◽  
Data Source

Digital elevation models (DEMs) and height measurements are broadly used in environmental studies. Two common elevation sources are the Ice Cloud and land elevation Satellite (ICESat), which acquired laser range measurements with the Geoscience Laser Altimeter System (GLAS) across the globe and elevation data from the Shuttle Radar Topography Mission (SRTM). Current developments of small unmanned aerial vehicles (UAV) provide the opportunity to collect aerial images of remote areas at a high spatial resolution. These can be further processed to digital surface models by stereophotogrammetry and provide a reliable data source to evaluate coarse scale Digital Elevation Models (DEMs). <br><br> This study compares ICESat/GLAS and SRTM90 elevation data against photogrammetric terrain heights within GLAS footprints on high altitudes on the East Tibetan Plateau. Without vegetation-bias, we were able to examine height differences under different topographic conditions and of different acquisition dates. Several resampling techniques were applied to SRTM90 data and averaged height within each footprint was calculated. ICESat/GLAS heights (n = 148) are most similar to UAV data based elevations with an averaged difference of &minus;0.8m ±3.1m. Results furthermore indicate the validity of ICESat/GLAS heights, which are usually removed from analyses by applying different quality flags. Smallest difference of SRTM90 to UAV based heights could be observed by a natural neighbour resampling technique (averaged 3.6m ±14m), whereat other techniques achieved quite similar results. It can be confirmed that within a range of 3,800&ndash;4,200m above mean sea level the ICESat/GLAS heights are a precise source to determine elevation at footprint geolocation.

scholarly journals A Relief Dependent Evaluation of Digital Elevation Models on Different Scales for Northern Chile

2019 ◽  
Vol 8 (10) ◽  
pp. 430 ◽  
Author(s):  
Kramm ◽  
Hoffmeister
Keyword(s):  
High Resolution ◽  
Laser Scanning ◽  
Thermal Emission ◽  
Comprehensive Evaluation ◽  
Digital Elevation Models ◽  
Shuttle Radar Topography Mission ◽  
Northern Chile ◽  
Digital Elevation ◽  
Elevation Data ◽  
Position Index

Many geoscientific computations are directly influenced by the resolution and accuracy of digital elevation models (DEMs). Therefore, knowledge about the accuracy of DEMs is essential to avoid misleading results. In this study, a comprehensive evaluation of the vertical accuracy of globally available DEMs from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Shuttle Radar Topography Mission (SRTM), Advanced Land Observing Satellite (ALOS) World 3D and TanDEM-X WorldDEM™ was conducted for a large region in Northern Chile. Additionally, several very high-resolution DEM datasets were derived from Satellite Pour l’Observation de la Terre (SPOT) 6/7 and Pléiades stereo satellite imagery for smaller areas. All datasets were evaluated with three reference datasets, namely elevation points from both Ice, Cloud, and land Elevation (ICESat) satellites, as well as very accurate high-resolution elevation data derived by unmanned aerial vehicle (UAV)-based photogrammetry and terrestrial laser scanning (TLS). The accuracy was also evaluated with regard to the existing relief by relating the accuracy results to slope, terrain ruggedness index (TRI) and topographic position index (TPI). For all datasets with global availability, the highest overall accuracies are reached by TanDEM-X WorldDEM™ and the lowest by ASTER Global DEM (GDEM). On the local scale, Pléiades DEMs showed a slightly higher accuracy as SPOT imagery. Generally, accuracy highly depends on topography and the error is rising up to four times for high resolution DEMs and up to eight times for low-resolution DEMs in steeply sloped terrain compared to flat landscapes.

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