A digital elevation model of the Antarctic ice sheet derived from ERS-1 altimeter data and comparison with terrestrial measurements

The launch of ERS-1 provides coverage, by satellite altimetry, of 80% of the Antarctic ice sheet, allowing topographic mapping of areas which previously had a dearth of accurate elevation data. Four 35 d repeat cycles of fastdelivery altimeter data were used in this study, comprising a total of approximately 1000000 height estimates. About 40% of these were rejected during a careful filtering procedure designed to remove erroneous values caused by poor tracking or complete loss of the returned echo. The OSU-91A geopotential model was used to convert ellipsoidal elevations to geoidal values. Corrections for surface slope were applied and a Digital Elevation Model (DEM) was produced with a grid spacing of 20km.The precision of the data was assessed from an analysis of crossing points of ascending and descending tracks. For 43864 cross-overs, the standard deviation was 6.8m. Regional biases associated with geoid, orbit and topography-induced errors reduce the accuracy of the height measurements. This was assessed by a comparison with ground-survey data. The DEM was compared with a 700km levelling survey, with an accuracy ranging from 1 to 5m, from the Lambert Glacier basin region (≈73° S, 55° E). The mean difference was found to be-1.6m with a standard deviation of 14m. A similar result was obtained for a 600km traverse line in Wilkes Land (75° S,≈1l0° E).The DEM was then compared with a digitized version of the Scott Polar Research Institute (SPRI) Antarctic folio map. This map was derived from orthometric measurements of surface elevation, primarily from pressure altimetry. Differences in excess of 300 m were observed between the two data sets. Only 37% of the region covered showed agreement to better than 50m, and a significant proportion ofthis was composed of the Ross and Filchner-Ronne Ice Shelves. The largest discrepancies occurred in marginal areas where there is poor coverage by both satellite altimetry and terrestrial data. Inland, significant differences were also found.

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Identifying areas of low-profile ice sheet and outcrop damming in the Antarctic ice sheet by ERS-1 satellite altimetry

Annals of Glaciology ◽

10.3189/1998aog27-1-1-6 ◽

1998 ◽

Vol 27 ◽

pp. 1-6 ◽

Cited By ~ 8

Author(s):

David G. Vaughan ◽

Jonathan L. Bamber

Keyword(s):

Satellite Altimetry ◽

Ice Sheet ◽

Surface Elevation ◽

Two Dimensional ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Continental Scale ◽

Low Profile ◽

Elevation Model ◽

The Antarctic

A digital elevation model (DEM) of the surface of the Antarctic ice sheet is compared with a simple two-dimensional ice-flow model to illuminate gross distortions (>500 m) of the ice-surface elevation. We use a DEM derived from ERS-1 satellite altimetry, airborne data and TWERLE balloon data. This is compared with an ice-sheet elevation model generated by applying theoretical surface elevations, calculated for two-dimensional ice flow, to isolines of distance from the grounding line (continentality). The model is scaled using only one parameter, to match the measured surface elevation at Dome Argus. The model is far from rigorous, violating continuity conditions, ignoring variations in surface mass balance and temperature, and assuming uniform basal conditions. However, the comparison of model and observed surface elevations is illuminating in terms of the behaviour of the ice sheet at a continental scale. Across the ice sheet the rms difference between modelled elevation and the DEM is around 300 m, but much of this results from isolated areas of much greater disagreement. We ascribe these gross differences to the effects of basal conditions. in four areas, the observed surface is more than 500 m higher than the modelled surface. Most of these are immediately upstream of substantial areas of rock outcrop and are caused by the damming effect of these mountain ranges. in nine areas, the measured surface is more than 500 m lower than predicted. Eight of these areas, in West Antarctica and the Lambert Glacier basin, are associated with suspected areas of basal sliding. The ninth is an area of 250 000 km2 in East Antarctica not previously noted as having unusual flow characteristics, but for which very few-data exist. We speculate that this area results from unusual basal conditions resulting in a low-profile ice sheet. A low-profile ice sheet of this size with in the East Antarctic ice sheet indicates that basal conditions are perhaps more variable than previously thought.

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Identifying areas of low-profile ice sheet and outcrop damming in the Antarctic ice sheet by ERS-1 satellite altimetry

Annals of Glaciology ◽

10.1017/s0260305500017146 ◽

1998 ◽

Vol 27 ◽

pp. 1-6 ◽

Cited By ~ 4

Author(s):

David G. Vaughan ◽

Jonathan L. Bamber

Keyword(s):

Satellite Altimetry ◽

Ice Sheet ◽

Surface Elevation ◽

Two Dimensional ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Continental Scale ◽

Low Profile ◽

Elevation Model ◽

The Antarctic

A digital elevation model (DEM) of the surface of the Antarctic ice sheet is compared with a simple two-dimensional ice-flow model to illuminate gross distortions (>500 m) of the ice-surface elevation. We use a DEM derived from ERS-1 satellite altimetry, airborne data and TWERLE balloon data. This is compared with an ice-sheet elevation model generated by applying theoretical surface elevations, calculated for two-dimensional ice flow, to isolines of distance from the grounding line (continentality). The model is scaled using only one parameter, to match the measured surface elevation at Dome Argus. The model is far from rigorous, violating continuity conditions, ignoring variations in surface mass balance and temperature, and assuming uniform basal conditions. However, the comparison of model and observed surface elevations is illuminating in terms of the behaviour of the ice sheet at a continental scale. Across the ice sheet the rms difference between modelled elevation and the DEM is around 300 m, but much of this results from isolated areas of much greater disagreement. We ascribe these gross differences to the effects of basal conditions. in four areas, the observed surface is more than 500 m higher than the modelled surface. Most of these are immediately upstream of substantial areas of rock outcrop and are caused by the damming effect of these mountain ranges. in nine areas, the measured surface is more than 500 m lower than predicted. Eight of these areas, in West Antarctica and the Lambert Glacier basin, are associated with suspected areas of basal sliding. The ninth is an area of 250 000 km2 in East Antarctica not previously noted as having unusual flow characteristics, but for which very few-data exist. We speculate that this area results from unusual basal conditions resulting in a low-profile ice sheet. A low-profile ice sheet of this size with in the East Antarctic ice sheet indicates that basal conditions are perhaps more variable than previously thought.

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A new 1 km digital elevation model of Antarctica derived from combined radar and laser data – Part 2: Validation and error estimates

The Cryosphere ◽

10.5194/tc-3-113-2009 ◽

2009 ◽

Vol 3 (1) ◽

pp. 113-123 ◽

Cited By ~ 36

Author(s):

J. A. Griggs ◽

J. L. Bamber

Keyword(s):

Digital Elevation Model ◽

Satellite Data ◽

Ice Sheet ◽

Multiple Linear Regression Model ◽

Altimeter Data ◽

Laser Altimeter ◽

Digital Elevation ◽

Surface Slopes ◽

Wide Range ◽

Elevation Model

Abstract. We have developed a new digital elevation model (DEM) of Antarctica from a combination of satellite radar and laser altimeter data. Here, we assess the accuracy of the DEM by comparison with airborne altimeter data from four campaigns covering a wide range of surface slopes and ice sheet regions. Root mean squared (RMS) differences varied from 4.75 m, when compared to a densely gridded airborne dataset over the Siple Coast region of West Antarctica to 33.78 m when compared to a more limited dataset over the Antarctic Peninsula where surface slopes are high and the across track spacing of the satellite data is relatively large. The airborne data sets were employed to produce an error map for the DEM by developing a multiple linear regression model based on the variables known to influence errors in the DEM. Errors were found to correlate highly with surface slope, roughness and density of satellite data points. Errors ranged from typically ~1 m over the ice shelves to between about 2 and 6 m for the majority of the grounded ice sheet. In the steeply sloping margins, along the Peninsula and mountain ranges the estimated error is several tens of metres. Less than 2% of the area covered by the satellite data had an estimated random error greater than 20 m.

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A new 1 km digital elevation model of Antarctica derived from combined radar and laser data – Part 2: Validation and error estimates

The Cryosphere Discussions ◽

10.5194/tcd-2-843-2008 ◽

2008 ◽

Vol 2 (5) ◽

pp. 843-872 ◽

Cited By ~ 2

Author(s):

J. A. Griggs ◽

J. L. Bamber

Keyword(s):

Digital Elevation Model ◽

Satellite Data ◽

Ice Sheet ◽

Multiple Linear Regression Model ◽

Altimeter Data ◽

Laser Altimeter ◽

Digital Elevation ◽

Surface Slopes ◽

Wide Range ◽

Elevation Model

Abstract. We have developed a new digital elevation model (DEM) of Antarctica from a combination of satellite radar and laser altimeter data. Here, we assess the accuracy of the DEM by comparison with airborne altimeter data from four campaigns covering a wide range of surface slopes and ice sheet regions. RMS differences varied from 4.84 m, when compared to a densely gridded airborne dataset over the Siple Coast region of West Antarctica to 29.28 m when compared to a more limited dataset over the Antarctic Peninsula where surface slopes are high and the across track spacing of the satellite data is relatively large. The airborne data sets were employed to produce an error map for the DEM by developing a multiple linear regression model based on the variables known to influence errors in the DEM. Errors were found to correlate highly with surface slope, roughness and density of satellite data points. Errors ranged from typically ~1 m over the ice shelves to between about 4 and 10 m for the majority of the grounded ice sheet. In the steeply sloping margins, along the Peninsula and mountain ranges the estimated error is several tens of metres. Slightly less than 7% of the area covered by the satellite data had an estimated random error greater than 20 m.

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Precise computation of the direct and indirect topographic effects of Helmert's 2nd method of condensation using SRTM30 digital elevation model

Journal of Geodetic Science ◽

10.2478/v10156-011-0009-8 ◽

2011 ◽

Vol 1 (4) ◽

pp. 305-312 ◽

Cited By ~ 2

Author(s):

Y. Wang

Keyword(s):

Standard Deviation ◽

Digital Elevation Model ◽

Outer Zone ◽

Mean Value ◽

Constant Density ◽

Topographic Effects ◽

Topographic Effect ◽

Digital Elevation ◽

The Mean ◽

Elevation Model

Precise computation of the direct and indirect topographic effects of Helmert's 2nd method of condensation using SRTM30 digital elevation modelThe direct topographic effect (DTE) and indirect topographic effect (ITE) of Helmert's 2nd method of condensation are computed using the digital elevation model (DEM) SRTM30 in 30 arc-seconds globally. The computations assume a constant density of the topographic masses. Closed formulas are used in the inner zone of half degree, and Nagy's formulas are used in the innermost column to treat the singularity of integrals. To speed up the computations, 1-dimensional fast Fourier transform (1D FFT) is applied in outer zone computations. The computation accuracy is limited to 0.1 mGal and 0.1cm for the direct and indirect effect, respectively.The mean value and standard deviation of the DTE are -0.8 and ±7.6 mGal over land areas. The extreme value -274.3 mGal is located at latitude -13.579° and longitude 289.496°, at the height of 1426 meter in the Andes Mountains. The ITE is negative everywhere and has its minimum of -235.9 cm at the peak of Himalayas (8685 meter). The standard deviation and mean value over land areas are ±15.6 cm and -6.4 cm, respectively. Because the Stokes kernel does not contain the zero and first degree spherical harmonics, the mean value of the ITE can't be compensated through the remove-restore procedure under the Stokes-Helmert scheme, and careful treatment of the mean value in the ITE is required.

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A new 100-m Digital Elevation Model of the Antarctic Peninsula derived from ASTER Global DEM: methods and accuracy assessment

Earth System Science Data ◽

10.5194/essd-4-129-2012 ◽

2012 ◽

Vol 4 (1) ◽

pp. 129-142 ◽

Cited By ~ 49

Author(s):

A. J. Cook ◽

T. Murray ◽

A. Luckman ◽

D. G. Vaughan ◽

N. E. Barrand

Keyword(s):

Digital Elevation Model ◽

Antarctic Peninsula ◽

Accuracy Assessment ◽

Correction Method ◽

Pixel Size ◽

Aster Gdem ◽

Digital Elevation ◽

Vertical Accuracy ◽

Elevation Model ◽

The Antarctic

Abstract. A high resolution surface topography Digital Elevation Model (DEM) is required to underpin studies of the complex glacier system on the Antarctic Peninsula. A complete DEM with better than 200 m pixel size and high positional and vertical accuracy would enable mapping of all significant glacial basins and provide a dataset for glacier morphology analyses. No currently available DEM meets these specifications. We present a new 100-m DEM of the Antarctic Peninsula (63–70° S), based on ASTER Global Digital Elevation Model (GDEM) data. The raw GDEM products are of high-quality on the rugged terrain and coastal-regions of the Antarctic Peninsula and have good geospatial accuracy, but they also contain large errors on ice-covered terrain and we seek to minimise these artefacts. Conventional data correction techniques do not work so we have developed a method that significantly improves the dataset, smoothing the erroneous regions and hence creating a DEM with a pixel size of 100 m that will be suitable for many glaciological applications. We evaluate the new DEM using ICESat-derived elevations, and perform horizontal and vertical accuracy assessments based on GPS positions, SPOT-5 DEMs and the Landsat Image Mosaic of Antarctica (LIMA) imagery. The new DEM has a mean elevation difference of −4 m (&pm; 25 m RMSE) from ICESat (compared to −13 m mean and &pm;97 m RMSE for the original ASTER GDEM), and a horizontal error of less than 2 pixels, although elevation accuracies are lower on mountain peaks and steep-sided slopes. The correction method significantly reduces errors on low relief slopes and therefore the DEM can be regarded as suitable for topographical studies such as measuring the geometry and ice flow properties of glaciers on the Antarctic Peninsula. The DEM is available for download from the NSIDC website: http://nsidc.org/data/nsidc-0516.html (doi:10.5060/D47P8W9D).

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A new approach to estimate ice dynamic rates using satellite observations in East Antarctica

10.5194/tc-2016-269 ◽

2016 ◽

Author(s):

Bianca Kallenberg ◽

Paul Tregoning ◽

Janosch F. Hoffmann ◽

Rhys Hawkins ◽

Anthony Purcell ◽

...

Keyword(s):

Mass Balance ◽

Satellite Altimetry ◽

Ice Sheet ◽

East Antarctica ◽

Surface Mass Balance ◽

Antarctic Ice Sheet ◽

Surface Mass ◽

Elevation Changes ◽

Ice Sheet Mass Balance ◽

The Antarctic

Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It's often been assumed that changes in ice dynamic rates only need to be considered when assessing long term ice sheet mass balance; however, two decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about changes in ice dynamic rates are still limited, especially in East Antarctica. Without understanding ice dynamic rates it is not possible to properly assess changes in ice sheet mass balance, surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice dynamic rates by removing modelled rates of surface mass balance, firn compaction and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of ice dynamic rates by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction and ice dynamic rates can be modelled and correlate with observed elevation changes from satellite altimetry.

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The influence of Antarctic ice loss on polar motion: an assessment based on GRACE and multi-mission satellite altimetry

Earth Planets and Space ◽

10.1186/s40623-021-01403-6 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Franziska Göttl ◽

Andreas Groh ◽

Michael Schmidt ◽

Ludwig Schröder ◽

Florian Seitz

Keyword(s):

Gravity Field ◽

Polar Motion ◽

Satellite Altimetry ◽

Motion Vector ◽

Ice Sheet ◽

Position Vector ◽

Random Errors ◽

Excitation Functions ◽

Antarctic Ice Sheet ◽

The Antarctic

AbstractIncreasing ice loss of the Antarctic Ice Sheet (AIS) due to global climate change affects the orientation of the Earth’s spin axis with respect to an Earth-fixed reference system (polar motion). Here the contribution of the decreasing AIS to the excitation of polar motion is quantified from precise time variable gravity field observations of the Gravity Recovery and Climate Experiment (GRACE) and from measurements of the changing ice sheet elevation from altimeter satellites. While the GRACE gravity field models need to be reduced by noise and leakage effects from neighboring subsystems, the ice volume changes observed by satellite altimetry have to be converted into ice mass changes. In this study we investigate how much individual gravimetry and altimetry solutions differ from each other. We show that due to combination of individual solutions systematic and random errors of the data processing can be reduced and the robustness of the geodetic derived AIS polar motion excitations can be increased. We investigate the interannual variability of the Antarctic polar motion excitation functions by means of piecewise linear trends. We find that the long-term behavior of the three ice sheet subregions: EAIS (East Antarctic Ice Sheet), WAIS (West Antarctic Ice Sheet) and APIS (Antarctic Peninsula Ice Sheet) is quite different. While APIS polar motion excitations show no significant interannual variations during the study period $$2003-2015$$ 2003 - 2015 , the trend of the WAIS and EAIS polar motion excitations increased in 2006 and again in 2009 while it started slightly to decline in 2013. AIS mass changes explain about $$45\%$$ 45 % of the observed magnitude of the polar motion vector (excluding glacial isosatic adjustment). They cause the pole position vector to drift along $$59^{\circ }$$ 59 ∘ East longitude with an amplitude of 2.7 mas/yr. Thus the contribution of the AIS has to be considered to close the budget of the geophysical excitation functions of polar motion.

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An Improved Digital Elevation Model of the Lunar Mons Rümker Region Based on Multisource Altimeter Data

Remote Sensing ◽

10.3390/rs10091442 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1442 ◽

Cited By ~ 3

Author(s):

Fei Li ◽

Chang Zhu ◽

Weifeng Hao ◽

Jianguo Yan ◽

Mao Ye ◽

...

Keyword(s):

Digital Elevation Model ◽

Ground Truth ◽

Horizontal Resolution ◽

Altimeter Data ◽

Laser Altimeter ◽

Lunar Landing ◽

Data Processing Method ◽

Digital Elevation ◽

Lunar Reconnaissance Orbiter ◽

Elevation Model

Mons Rümker is the primary candidate region for the lunar landing mission of Chang’E-5. We propose a data processing method that combines multisource altimeter data and we developed an improved digital elevation model (DEM) of the Mons Rümker region with a horizontal resolution of 256 pixels per degree. The lunar orbiter laser altimeter (LOLA) onboard the lunar reconnaissance orbiter (LRO) acquired 884 valid orbital benchmark data with a high precision. A special crossover adjustment of 156 orbital profiles from the Chang’E-1 laser altimeter (LAM) and 149 orbital profiles from the SELenological and ENgineering Explorer (SELENE) laser altimeter (LALT) was applied. The radial residual root mean square (RMS) of the LAM was reduced from 154.83 ± 43.60 m to 14.29 ± 27.84 m and that of the LALT was decreased from 3.50 ± 5.0 m to 2.75 ± 4.4 m. We used the adjusted LAM and LALT data to fill the LOLA gaps and created the merged LOLA + LAM and LOLA + LALT DEMs. The merged LOLA + LAM DEM showed distortions because of the horizontal geolocation errors in the LAM data. The merged LOLA + LALT DEM was closer to the ground truth than the LOLA-only DEM when validated with the images of the LRO camera (LROC).

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