scholarly journals Airborne Validation of ICESat-2 ATLAS Data Over Crevassed Surfaces and Other Complex Glacial Environments: Results From Experiments of Laser Altimeter and Kinematic GPS Data Collection From a Helicopter Over a Surging Arctic Glacier (Negribreen, Svalbard)

2021 ◽  
Author(s):  
Ute Christina Herzfeld ◽  
Matthew Lawson ◽  
Thomas Trantow ◽  
Thomas Nylen
Keyword(s):  
Data Collection ◽  
Altimeter Data ◽  
Gps Data ◽  
Laser Altimeter ◽  
Kinematic Gps ◽  
Atlas Data ◽  
Height Determination ◽  
Ice Surface ◽  
Airborne Laser ◽  
Along Track

The topic of this paper is the airborne evaluation of ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS) measurement capabilities and surface-height-determination over crevassed glacial terrain, with a focus on the geodetical accuracy of geophysical data collected from a helicopter. To obtain surface heights over crevassed and otherwise complex ice surface, ICESat-2 data are analyzed using the density-dimension algorithm for ice surfaces (DDA-ice), which yields surface heights at the nominal 0.7~m along-track spacing of ATLAS data. As the result of an ongoing surge, Negribreen, Svalbard, provided an ideal situation for the validation objectives in 2018 and 2019, because many different crevasse types and morphologically complex ice surfaces existed in close proximity. Airborne geophysical data, including laser altimeter data (profilometer data at 905~nm frequency), differential Global Positioning System (GPS), Inertial Measurement Unit (IMU) data, on-board-time-lapse imagery and photographs, were collected during two campaigns in summers of 2018 and 2019. Airborne experiment setup, geodetical correction and data processing steps are described here. To date, there is relatively little knowledge of the geodetical accuracy that can be obtained from kinematic data collection from a helicopter. Our study finds that (1)~Kinematic GPS data collection with correction in post-processing yields higher accuracies than Real-Time-Kinematic (RTK) data collection. (2)~Processing of only the rover data using the Natural Resources Canada Spatial Reference System Precise Point Positioning (CSRS-PPP) software is sufficiently accurate for the sub-satellite validation purpose. (3)~Distances between ICESat-2 ground tracks and airborne ground tracks were generally better than 25~m, while distance between predicted and actual ICESat-2 ground track was on the order of 9~m, which allows direct comparison of ice-surface heights and spatial statistical characteristics of crevasses from the satellite and airborne measurements. (4)~The Lasertech Universal Laser System (ULS), operated at up to 300~m above ground level, yields full return frequency (400~Hz) and 0.06-0.08~m on-ice along-track spacing of height measurements. (5)~Cross-over differences of airborne laser altimeter data are 0.1918 $\pm$ 2.385~m along straight paths over generally crevassed terrain, which implies a precision of approximately 2.4~m for ICESat-2 validation experiments. (6)~In summary, the comparatively light-weight experiment setup of a suite of small survey equipment mounted on a Eurocopter (Helicopter AS-350) and kinematic GPS data analyzed in post-processing using CSRS-PPP leads to high accuracy repeats of the ICESat-2 tracks. The technical results (1)-(6) indicate that direct comparison of ice-surface heights and crevasse depths from the ICESat-2 and airborne laser altimeter data is warranted. The final result of the validation is that ICESat-2 ATLAS data, analyzed with the DDA-ice, facilitate surface-height determination over crevassed terrain, in good agreement with airborne data, including spatial characteristics, such as surface roughness, crevasse spacing and depth, which are key informants on the deformation and dynamics of a glacier during surge.

scholarly journals Airborne Validation of ICESat-2 ATLAS Data Over Crevassed Surfaces and Other Complex Glacial Environments: Results From Experiments of Laser Altimeter and Kinematic GPS Data Collection From a Helicopter Over a Surging Arctic Glacier (Negribreen, Svalbard)

2021 ◽  
Author(s):  
Ute Christina Herzfeld ◽  
Matthew Lawson ◽  
Thomas Trantow ◽  
Thomas Nylen
Keyword(s):  
Data Collection ◽  
Altimeter Data ◽  
Gps Data ◽  
Laser Altimeter ◽  
Kinematic Gps ◽  
Atlas Data ◽  
Height Determination ◽  
Ice Surface ◽  
Airborne Laser ◽  
Along Track

The topic of this paper is the airborne evaluation of ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS) measurement capabilities and surface-height-determination over crevassed glacial terrain, with a focus on the geodetical accuracy of geophysical data collected from a helicopter. To obtain surface heights over crevassed and otherwise complex ice surface, ICESat-2 data are analyzed using the density-dimension algorithm for ice surfaces (DDA-ice), which yields surface heights at the nominal 0.7~m along-track spacing of ATLAS data. As the result of an ongoing surge, Negribreen, Svalbard, provided an ideal situation for the validation objectives in 2018 and 2019, because many different crevasse types and morphologically complex ice surfaces existed in close proximity. Airborne geophysical data, including laser altimeter data (profilometer data at 905~nm frequency), differential Global Positioning System (GPS), Inertial Measurement Unit (IMU) data, on-board-time-lapse imagery and photographs, were collected during two campaigns in summers of 2018 and 2019. Airborne experiment setup, geodetical correction and data processing steps are described here. To date, there is relatively little knowledge of the geodetical accuracy that can be obtained from kinematic data collection from a helicopter. Our study finds that (1)~Kinematic GPS data collection with correction in post-processing yields higher accuracies than Real-Time-Kinematic (RTK) data collection. (2)~Processing of only the rover data using the Natural Resources Canada Spatial Reference System Precise Point Positioning (CSRS-PPP) software is sufficiently accurate for the sub-satellite validation purpose. (3)~Distances between ICESat-2 ground tracks and airborne ground tracks were generally better than 25~m, while distance between predicted and actual ICESat-2 ground track was on the order of 9~m, which allows direct comparison of ice-surface heights and spatial statistical characteristics of crevasses from the satellite and airborne measurements. (4)~The Lasertech Universal Laser System (ULS), operated at up to 300~m above ground level, yields full return frequency (400~Hz) and 0.06-0.08~m on-ice along-track spacing of height measurements. (5)~Cross-over differences of airborne laser altimeter data are 0.1918 $\pm$ 2.385~m along straight paths over generally crevassed terrain, which implies a precision of approximately 2.4~m for ICESat-2 validation experiments. (6)~In summary, the comparatively light-weight experiment setup of a suite of small survey equipment mounted on a Eurocopter (Helicopter AS-350) and kinematic GPS data analyzed in post-processing using CSRS-PPP leads to high accuracy repeats of the ICESat-2 tracks. The technical results (1)-(6) indicate that direct comparison of ice-surface heights and crevasse depths from the ICESat-2 and airborne laser altimeter data is warranted. The final result of the validation is that ICESat-2 ATLAS data, analyzed with the DDA-ice, facilitate surface-height determination over crevassed terrain, in good agreement with airborne data, including spatial characteristics, such as surface roughness, crevasse spacing and depth, which are key informants on the deformation and dynamics of a glacier during surge.

scholarly journals Alignment determination of the Hayabusa2 laser altimeter (LIDAR)

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.

scholarly journals Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012

2014 ◽  
Vol 60 (221) ◽  
pp. 489-499 ◽  
Author(s):  
Andreas Münchow ◽  
Laurie Padman ◽  
Helen A. Fricker
Keyword(s):  
Mass Loss ◽  
Three Dimensional ◽  
Greenland Ice Sheet ◽  
Altimeter Data ◽  
Ice Shelf ◽  
Laser Altimetry ◽  
Laser Altimeter ◽  
Airborne Laser ◽  
Tracking Surface ◽  
Basal Melting

AbstractPetermann Gletscher, northwest Greenland, drains 4% of the Greenland ice sheet into Nares Strait. Its floating ice shelf retreated from 81 to 48 km in length during two large calving events in 2010 and 2012. We document changes in the three-dimensional ice-shelf structure from 2000 to 2012, using repeated tracks of airborne laser altimetry and ice radio-echo sounding, ICESat laser altimetry and MODIS visible imagery. The recent ice-shelf velocity, measured by tracking surface features between flights in 2010 and 2011, is ~1.25 km a−1, ~15–30% faster than estimates made before 2010. The steady- state along-flow ice divergence represents 6.3 Gta−1 mass loss through basal melting (~5Gta−1) and surface melting and sublimation (~1.0Gta−1). Airborne laser altimeter data reveal thinning, both along a thin central channel and on the thicker ambient ice shelf. From 2007 to 2010 the ice shelf thinned by ~5 m a−1, which represents a non-steady mass loss of ~4.1 Gta−1. We suggest that thinning in the basal channels structurally weakened the ice shelf and may have played a role in the recent calving events.

A Method of Extracting High-Accuracy Elevation Control Points from ICESat-2 Altimetry Data

2021 ◽  
Vol 87 (11) ◽  
pp. 821-830
Author(s):  
Binbin Li ◽  
Huan Xie ◽  
Shijie Liu ◽  
Xiaohua Tong ◽  
Hong Tang ◽  
...  
Keyword(s):  
Large Scale ◽  
Comprehensive Evaluation ◽  
Photon Counting ◽  
High Accuracy ◽  
Airborne Lidar ◽  
Altimeter Data ◽  
Control Points ◽  
Laser Altimeter ◽  
Terrain Elevation ◽  
Along Track

Due to its high ranging accuracy, spaceborne laser altimetry technology can improve the accuracy of satellite stereo mapping without ground control points. In the past, full-waveform ICE, CLOUD, and Land Elevation Satellite (ICESat) laser altimeter data have been used as one of the main data sources for global elevation control. As a second-generation satellite, ICESat-2 is equipped with an altimeter using photon counting mode. This can further improve the application capability for stereo mapping because of the six laser beams with high along-track repetition frequency, which can provide more detailed ground contour descriptions. Previous studies have addressed how to extract high-accuracy elevation control points from ICESat data. However, these methods cannot be directly applied to ICESat-2 data because of the different modes of the laser altimeters. Therefore, in this paper, we propose a method using comprehensive evaluation labels that can extract high-accuracy elevation control points that meet the different level elevation accuracy requirements for large scale mapping from the ICESat-2 land-vegetation along-track product. The method was verified using two airborne lidar data sets. In flat, hilly, and mountainous areas, by using our method to extract the terrain elevation, the root-mean-square error of elevation control points decrease from 1.249–2.094 m, 2.237–3.225 m, and 2.791–4.822 m to 0.262–0.429 m, 0.484–0.596 m, and 0.611–1.003 m, respectively. The results show that the extraction elevations meet the required accuracy for large scale mapping.

scholarly journals Morphology of basaltic lava channels during the Mt. Etna September 2004 eruption from airborne laser altimeter data

2005 ◽  
Vol 32 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Francesco Mazzarini ◽  
Maria Teresa Pareschi ◽  
Massimiliano Favalli ◽  
Ilaria Isola ◽  
Simone Tarquini ◽  
...  
Keyword(s):  
Altimeter Data ◽  
Basaltic Lava ◽  
Laser Altimeter ◽  
Airborne Laser ◽  
Mt Etna

scholarly journals Bering Glacier surge 2011: analysis of laser altimeter data

2013 ◽  
Vol 54 (63) ◽  
pp. 158-170 ◽  
Author(s):  
Ute C. Herzfeld ◽  
Brian McDonald ◽  
Maciej Stachura ◽  
Robert Griffin Hale ◽  
Phillip Chen ◽  
...  
Keyword(s):  
Large Scale ◽  
Altimeter Data ◽  
Small Scale ◽  
Rapid Progression ◽  
Laser Altimeter ◽  
Reservoir Area ◽  
Airborne Laser ◽  
Bering Glacier ◽  
Change Characteristics ◽  
Elevation Changes

AbstractThe Bering Glacier–Bagley Icefield system in Alaska is currently surging (2011). Large-scale elevation changes and small-scale elevation-change characteristics are investigated to understand surge progression, especially mass transport from the pre-surge reservoir area to the receiving area and propagation of the kinematic surge wave as manifested in heavy crevassing characteristic of rapid, brittle deformation. This analysis is based on airborne laser altimeter data collected over Bering Glacier in September 2011. Results include the following: (1) Maximal crevasse depth is 60 m, reached in a rift that separates two deformation domains, indicative of two different flow regimes. Otherwise surge crevasse depth reaches 20–30 m. (2) Characteristic parameters of structural provinces are derived by application of geostatistical classification. Parameters include significance and spacing of crevasses, surface roughness and crevasse-edge curvature (indicative of crevasse age). A classification based on these parameters serves to objectively discriminate structural provinces, indicative of surge progression down-glacier and up-glacier. (3) Elevation changes from 2011 and 2010 altimetry show 40–70 m surface lowering in the reservoir area in lower central Bering Glacier and 20–40m thickening near the front in Tashalich arm. Combining elevation changes with results of crevasse profilometry and pattern analysis, the rapid progression of the surge can be mathematically–physically reconstructed.

scholarly journals Sea-ice surface roughness estimates from airborne laser scanner and laser altimeter observations in Fram Strait and north of Svalbard

2015 ◽  
Vol 56 (69) ◽  
pp. 235-244 ◽  
Author(s):  
Justin F. Beckers ◽  
Angelika H.H. Renner ◽  
Gunnar Spreen ◽  
Sebastian Gerland ◽  
Christian Haas
Keyword(s):  
Surface Roughness ◽  
Sea Ice ◽  
Laser Scanner ◽  
Ice Thickness ◽  
Fram Strait ◽  
Laser Altimeter ◽  
Airborne Laser Scanner ◽  
Ice Surface ◽  
Airborne Laser ◽  
Ice Surface Roughness

AbstractWe present sea-ice surface roughness estimates, i.e. the standard deviation of relative surface elevation, in the Arctic regions of Fram Strait and the Nansen Basin north of Svalbard acquired by an airborne laser scanner and a single-beam laser altimeter in 2010. We compare the scanner to the altimeter and compare the differences between the two survey regions. We estimate and correct sensor roll from the scanner data using the hyperbolic response of the scanner over a flat surface. Measurement surveys had to be longer than 5 km north of Svalbard and longer than 15 km in Fram Strait before the statistical distribution in surface roughness from the scanner and altimeter became similar. The shape of the surface roughness probability distributions agrees with those of airborne electromagnetic induction measurements of ice thickness. The ice in Fram Strait had a greater mean surface roughness, 0.16 m vs 0.09 m, and a wider distribution in roughness values than the ice in the Nansen Basin. An increase in surface roughness with increasing ice thickness was observed over fast ice found in Fram Strait near the coast of Greenland but not for the drift ice.

scholarly journals Thickening of Jakobshavns Isbræ, West Greenland, measured by airborne laser altimetry

1995 ◽  
Vol 21 ◽  
pp. 259-262 ◽  
Author(s):  
R. Thomas ◽  
W. Rkabill ◽  
E. Frederick ◽  
K. Jezek
Keyword(s):  
Ice Sheet ◽  
Drainage Basins ◽  
Laser Altimeter ◽  
Additional Increase ◽  
Gps Navigation ◽  
Ice Surface ◽  
Airborne Laser ◽  
Global Positioning ◽  
Long Term Trends

NASA flights over southern Greenland in 1991, 1992 and 1993, using a scanning laser altimeter with Global Positioning System (GPS) navigation, have demonstrated a capability to measure ice-surface elevations to an accuracy of 10-15 cm. Flights over Jakobshavns Isbræ revealed winter thickening by several meters between September 1991 and April 1992. By July 1993, surface elevations showed a small additional increase, possibly associated with the cold 1992 summer. Data collected over the ice sheet east of Jakobshavns Isbræ show negligible change over the same period; but further south, at latitude 65 N, the western part of the ice sheet appears to have thickened by up to 2 m between 1980 and 1993. It is clear that such measurements must be continued over many years, both to quantify the effects of inter-annual variability and to measure long-term trends. To this end, we plan to complete a first survey of all major drainage basins on the ice sheet in May-June 1994, and then to resurvey all flight lines at 5a intervals, with more frequent flights over selected routes.

scholarly journals Rigorous GPS data-processing strategies for glaciological applications

2004 ◽  
Vol 50 (171) ◽  
pp. 601-607 ◽  
Author(s):  
Matt King
Keyword(s):  
Data Processing ◽  
Systematic Errors ◽  
Gps Data ◽  
Laser Altimeter ◽  
Thickness Change ◽  
Height Determination ◽  
Processing Strategies ◽  
Formal Error ◽  
Gps Processing ◽  
Processing Techniques

AbstractGlobal positioning system (GPS) data are now routinely used for many glaciological applications. In some common cases, systematic errors are unmodelled at the data-processing stage, although they are often presumed insignificant. In this paper, I investigate these assumptions for three different scenarios: (1) measurements on a moving glacier; (2) measurements on a floating ice shelf; and (3) precise height determination over large elevation ranges, such as for aircraft positioning in lidar/laser altimeter missions. In each case, systematic errors are shown to be present in the coordinate solutions that have a far greater magnitude than the formal error estimates produced by the GPS processing software, under certain conditions. If these coordinate biases go undetected, short- and long-term measurements of horizontal ice velocity or rates of ice-thickness change may be erroneous and the coordinates could not be expected to match rigorously processed data or results from different processing techniques. More rigorous processing strategies are discussed that allow for bias-free parameter estimation.

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