Precision and Accuracy of Satellite Radar and Laser Altimeter Data Over the Continental Ice Sheets

AbstractDetailed digital elevation models (DEMs) do not exist for much of the Greenland and Antartic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-radar interferometry uses the phase difference between pairs of synthetic aperture radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland, extending northward from just above Jakobshavns Isbræ. Comparison with а 76 km long line of airborne laser-altimeter data shows that We have achieved a relative accuracy of 2.5 m along the profile. These observations provide a detailed view of dynamically Supported topography near the margin of an ice sheet. In the final section We compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

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Measurement of ice-sheet topography using satellite-radar interferometry

Journal of Glaciology ◽

10.1017/s0022143000030483 ◽

1996 ◽

Vol 42 (140) ◽

pp. 10-22 ◽

Cited By ~ 93

Author(s):

Ian Joughin ◽

Dale Winebrenner ◽

Mark Fahnestock ◽

Ron Kwok ◽

William Krabill

Keyword(s):

Ice Sheets ◽

Ice Sheet ◽

Surface Displacement ◽

Horizontal Resolution ◽

Radar Interferometry ◽

Altimeter Data ◽

Laser Altimeter ◽

Digital Elevation ◽

Satellite Radar ◽

Ice Sheet Topography

Abstract Detailed digital elevation models (DEMs) do not exist for much of the Greenland and Antartic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-radar interferometry uses the phase difference between pairs of synthetic aperture radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland, extending northward from just above Jakobshavns Isbræ. Comparison with а 76 km long line of airborne laser-altimeter data shows that We have achieved a relative accuracy of 2.5 m along the profile. These observations provide a detailed view of dynamically Supported topography near the margin of an ice sheet. In the final section We compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

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A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data – Part 1: Data and methods

The Cryosphere ◽

10.5194/tc-3-101-2009 ◽

2009 ◽

Vol 3 (1) ◽

pp. 101-111 ◽

Cited By ~ 213

Author(s):

J. L. Bamber ◽

J. L. Gomez-Dans ◽

J. A. Griggs

Keyword(s):

Surface Expression ◽

Altimeter Data ◽

Grid Cells ◽

Satellite Mission ◽

Laser Altimeter ◽

Digital Elevation ◽

Spatial Coverage ◽

Laser Data ◽

Vertical Accuracy ◽

Satellite Radar

Abstract. Digital elevation models (DEMs) of the whole of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 32% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves – the Filchner-Ronne and Ross – where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

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A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data – Part 1: Data and methods

The Cryosphere Discussions ◽

10.5194/tcd-2-811-2008 ◽

2008 ◽

Vol 2 (5) ◽

pp. 811-841 ◽

Cited By ~ 6

Author(s):

J. L. Bamber ◽

J. L. Gomez-Dans ◽

J. A. Griggs

Keyword(s):

Surface Expression ◽

Altimeter Data ◽

Grid Cells ◽

Satellite Mission ◽

Laser Altimeter ◽

Digital Elevation ◽

Spatial Coverage ◽

Laser Data ◽

Vertical Accuracy ◽

Satellite Radar

Abstract. Digital elevation models (DEMs) of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 35% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves – the Filchner-Ronne and Ross – where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

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Alignment determination of the Hayabusa2 laser altimeter (LIDAR)

Earth Planets and Space ◽

10.1186/s40623-020-01342-8 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Hirotomo Noda ◽

Hiroki Senshu ◽

Koji Matsumoto ◽

Noriyuki Namiki ◽

Takahide Mizuno ◽

...

Keyword(s):

Altimeter Data ◽

Gravity Assist ◽

Laser Altimeter ◽

Trajectory Error ◽

Flight Data ◽

Camera Image ◽

Operation Period ◽

The Cross ◽

Along Track

AbstractIn this study, we determined the alignment of the laser altimeter aboard Hayabusa2 with respect to the spacecraft using in-flight data. Since the laser altimeter data were used to estimate the trajectory of the Hayabusa2 spacecraft, the pointing direction of the altimeter needed to be accurately determined. The boresight direction of the receiving telescope was estimated by comparing elevations of the laser altimeter data and camera images, and was confirmed by identifying prominent terrains of other datasets. The estimated boresight direction obtained by the laser link experiment in the winter of 2015, during the Earth’s gravity assist operation period, differed from the direction estimated in this study, which fell on another part of the candidate direction; this was not selected in a previous study. Assuming that the uncertainty of alignment determination of the laser altimeter boresight was 4.6 pixels in the camera image, the trajectory error of the spacecraft in the cross- and/or along-track directions was determined to be 0.4, 2.1, or 8.6 m for altitudes of 1, 5, or 20 km, respectively.

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An Adaptive Density-Based Model for Extracting Surface Returns From Photon-Counting Laser Altimeter Data

IEEE Geoscience and Remote Sensing Letters ◽

10.1109/lgrs.2014.2360367 ◽

2015 ◽

Vol 12 (4) ◽

pp. 726-730 ◽

Cited By ~ 24

Author(s):

Jiashu Zhang ◽

John Kerekes

Keyword(s):

Photon Counting ◽

Altimeter Data ◽

Laser Altimeter

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Last Glacial Maximum and Holocene Climate in CCSM3

Journal of Climate ◽

10.1175/jcli3748.1 ◽

2006 ◽

Vol 19 (11) ◽

pp. 2526-2544 ◽

Cited By ~ 413

Author(s):

Bette L. Otto-Bliesner ◽

Esther C. Brady ◽

Gabriel Clauzet ◽

Robert Tomas ◽

Samuel Levis ◽

...

Keyword(s):

Last Glacial Maximum ◽

Ice Sheets ◽

Ocean Model ◽

Arctic Sea Ice ◽

Glacial Maximum ◽

Climate System Model ◽

Last Glacial ◽

Global Cooling ◽

Climate Forcings ◽

Continental Ice Sheets

Abstract The climate sensitivity of the Community Climate System Model version 3 (CCSM3) is studied for two past climate forcings, the Last Glacial Maximum (LGM) and the mid-Holocene. The LGM, approximately 21 000 yr ago, is a glacial period with large changes in the greenhouse gases, sea level, and ice sheets. The mid-Holocene, approximately 6000 yr ago, occurred during the current interglacial with primary changes in the seasonal solar irradiance. The LGM CCSM3 simulation has a global cooling of 4.5°C compared to preindustrial (PI) conditions with amplification of this cooling at high latitudes and over the continental ice sheets present at LGM. Tropical sea surface temperature (SST) cools by 1.7°C and tropical land temperature cools by 2.6°C on average. Simulations with the CCSM3 slab ocean model suggest that about half of the global cooling is explained by the reduced LGM concentration of atmospheric CO2 (∼50% of present-day concentrations). There is an increase in the Antarctic Circumpolar Current and Antarctic Bottom Water formation, and with increased ocean stratification, somewhat weaker and much shallower North Atlantic Deep Water. The mid-Holocene CCSM3 simulation has a global, annual cooling of less than 0.1°C compared to the PI simulation. Much larger and significant changes occur regionally and seasonally, including a more intense northern African summer monsoon, reduced Arctic sea ice in all months, and weaker ENSO variability.

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Global Mapping and Analysis of the Structural Features in the Northern Smooth Plains of Mercury

10.5194/epsc2021-743 ◽

2021 ◽

Author(s):

marco cardinale ◽

Gaetano Di Achille ◽

David A.Vaz

Keyword(s):

Imaging System ◽

Structural Features ◽

Planetary Science ◽

Altimeter Data ◽

Normal Faults ◽

Laser Altimeter ◽

Volcanic Material ◽

Geological Map ◽

Dual Imaging

Orbital data from the Messenger spacecraft (1) reveal that part of the Mercury surface is covered by smooth plains, which are interpreted to be flood volcanic material across the planetary surface (2). In this work, we present a detailed geo-structural map of the northern smooth plains between&#160; latitudes 29&#176;N and 65&#176;N. Our 1:100.000-scale map is obtained semi-automatically, using an algorithm to map all scarps from a DEM (3,4) followed by visual inspection and classification in ArcGIS. We created a DEM&#160; using the raw MLA (Mercury Laser Altimeter) data (1) ,with 500 m/pix, and we used the Mercury Messenger MDIS (Mercury Dual Imaging System) (1,2) base map with 166m per pixel for the classification stage. With this approach, we mapped and characterized 51664 features on Mercury, creating a database with several morphometric attributes (e.g. length, azimuth, scarp height) which we will use to study the tectonic evolution of the smooth plains.&#160; In this way, we classified wrinkle ridges&#8217;s scarps, ghost craters, rim craters and central peaks. The morphometric parameters of the wrinkle ridges will&#160; be quantitatively analyzed, in order to characterizer the possible tectonic process that could have formed them. This map can be considered an enhancement for the north pole of the global geological map of Mercury (1, 5). &#160; References <ul> <li>Hawkins, S. E., III, et al. (2007), The Mercury Dual Imaging System on the MESSENGER spacecraft, Space Sci. Rev., 131, 247&#8211;338..&#160;</li> <li>Denevi, B. W., et al. (2013), The distribution and origin of smooth plains on Mercury, J. Geophys. Res. Planets, 118, 891&#8211;907, doi:10.1002/jgre.20075.</li> <li>Alegre Vaz, D. (2011). Analysis of a Thaumasia Planum rift through automatic mapping and strain characterization of normal faults. Planetary and Space Science, 59(11-12), 1210&#8211;1221. doi:10.1016/j.pss.2010.07.008&#160;.</li> <li>Vaz, D. A., Spagnuolo, M. G., & Silvestro, S. (2014). Morphometric and geometric characterization of normal faults on Mars. Earth and Planetary Science Letters, 401, 83&#8211;94. doi:10.1016/j.epsl.2014.05.022.</li> <li>Kinczyk, M. J., Prockter, L., Byrne, P., Denevi, B., Buczkowski, D., Ostrach, L., & Miller, E. (2019, September). The First Global Geological Map of Mercury. In EPSC-DPS Joint Meeting 2019 (Vol. 2019, pp. EPSC-DPS2019).</li> </ul>

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Error identification in orbital laser altimeter data by machine learning

10.5194/egusphere-egu21-14749 ◽

2021 ◽

Author(s):

Oliver Stenzel ◽

Robin Thor ◽

Martin Hilchenbach

Keyword(s):

Machine Learning ◽

High Performance ◽

Space Science ◽

Altimeter Data ◽

Laser Altimetry ◽

Error Identification ◽

Laser Altimeter ◽

Data Set ◽

Baseline Design ◽

Solar System Bodies

Orbital Laser altimeters deliver a plethora of data that is used to map planetary surfaces [1] and to understand interiors of solar system bodies [2]. Accuracy and precision of laser altimetry measurements depend on the knowledge of spacecraft position and pointing and on the instrument. Both are important for the retrieval of tidal parameters. In order to assess the quality of the altimeter retrievals, we are training and implementing an artificial neural network (ANN) to identify and exclude scans from analysis which yield erroneous data. The implementation is based on the PyTorch framework [3]. We are presenting our results for the MESSENGER Mercury Laser Altimeter (MLA) data set [4], but also in view of future analysis of the BepiColombo Laser Altimeter (BELA) data, which will arrive in orbit around Mercury in 2025 on board the Mercury Planetary Orbiter [5,6]. We further explore conventional methods of error identification and compare these with the machine learning results. Short periods of large residuals or large variation of residuals are identified and used to detect erroneous measurements. Furthermore, long-period systematics, such as those caused by slow variations in instrument pointing, can be modelled by including additional parameters. [1] Zuber, Maria T., David E. Smith, Roger J. Phillips, Sean C. Solomon, Gregory A. Neumann, Steven A. Hauck, Stanton J. Peale, et al. &#8216;Topography of the Northern Hemisphere of Mercury from MESSENGER Laser Altimetry&#8217;. Science 336, no. 6078 (13 April 2012): 217&#8211;20. https://doi.org/10.1126/science.1218805. [2] Thor, Robin N., Reinald Kallenbach, Ulrich R. Christensen, Philipp Gl&#228;ser, Alexander Stark, Gregor Steinbr&#252;gge, and J&#252;rgen Oberst. &#8216;Determination of the Lunar Body Tide from Global Laser Altimetry Data&#8217;. Journal of Geodesy 95, no. 1 (23 December 2020): 4. https://doi.org/10.1007/s00190-020-01455-8. [3] Paszke, Adam, Sam Gross, Francisco Massa, Adam Lerer, James Bradbury, Gregory Chanan, Trevor Killeen, et al. &#8216;PyTorch: An Imperative Style, High-Performance Deep Learning Library&#8217;. Advances in Neural Information Processing Systems 32 (2019): 8026&#8211;37. [4] Cavanaugh, John F., James C. Smith, Xiaoli Sun, Arlin E. Bartels, Luis Ramos-Izquierdo, Danny J. Krebs, Jan F. McGarry, et al. &#8216;The Mercury Laser Altimeter Instrument for the MESSENGER Mission&#8217;. Space Science Reviews 131, no. 1 (1 August 2007): 451&#8211;79. https://doi.org/10.1007/s11214-007-9273-4. [5] Thomas, N., T. Spohn, J. -P. Barriot, W. Benz, G. Beutler, U. Christensen, V. Dehant, et al. &#8216;The BepiColombo Laser Altimeter (BELA): Concept and Baseline Design&#8217;. Planetary and Space Science 55, no. 10 (1 July 2007): 1398&#8211;1413. https://doi.org/10.1016/j.pss.2007.03.003. [6] Benkhoff, Johannes, Jan van Casteren, Hajime Hayakawa, Masaki Fujimoto, Harri Laakso, Mauro Novara, Paolo Ferri, Helen R. Middleton, and Ruth Ziethe. &#8216;BepiColombo&#8212;Comprehensive Exploration of Mercury: Mission Overview and Science Goals&#8217;. Planetary and Space Science, Comprehensive Science Investigations of Mercury: The scientific goals of the joint ESA/JAXA mission BepiColombo, 58, no. 1 (1 January 2010): 2&#8211;20. https://doi.org/10.1016/j.pss.2009.09.020.

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Source, Transportation and Deposition of Debris on Arapaho Glacier, Front Range, Colorado, U.S.A.

Journal of Glaciology ◽

10.1017/s0022143000021936 ◽

1975 ◽

Vol 14 (72) ◽

pp. 407-420 ◽

Cited By ~ 36

Author(s):

Marith Jean Reheis

Keyword(s):

Ice Sheets ◽

Front Range ◽

Denudation Rate ◽

The Past ◽

Glacier Front ◽

Till Fabric ◽

Continental Ice Sheets

This study was undertaken to determine the sources of debris and methods of transportation and deposition in and on a small cirque glacier. Data were collected on the amount of debris, stone roundness, the presence of striations and polish, and till fabric. Lichenometry gave relative ages of the tills, and suggests that the Gannett Peak till is of at least three ages and probably overlies Audubon till.Debris originating from subglacial erosion can be differentiated from that from rockfall or avalanches on stone roundness, polish and striations. A maximum of 70% of the present glacial load derives from subglacial erosion, as compared to 88% during the Gannett Peak stade. Rockfall rates are 35-50 m3/year at present and were 290–485 m3/year during the Gannett Peak stade. Data on present-day processes and on the volume and age of Gannett Peak moraines can be used to make comparisons on present and past rates of denudation. The denudation rate in the cirque at present is 95–165 mm/1 000 year; in the past it was 4 920-8 160 mm/ 1 000 year. The denudation rate and the glacial effects on debris are comparable to rates from other glacial areas and effects on debris carried by valley glaciers and continental ice sheets.

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