The Greenland Ice Sheet is undergoing dramatic change. How the ice sheet continues to respond to ... more The Greenland Ice Sheet is undergoing dramatic change. How the ice sheet continues to respond to climate change has important ramifications for global climate and sea level rise, but the observation-based record of ice sheet change is extremely short. We use glacial-geologic techniques to determine the behavior of the Greenland Ice Sheet over longer timescales. In particular, we focus on the Holocene history of Jakobshavn Isbrae, one of the key ice streams on Greenland that is responsible for disproportionate mass loss of the Greenland Ice Sheet. Radiocarbon ages from basal lake sediments and 10Be exposure ages of bedrock spanning from the present ice margin to Disko Bugt, ~50 km west, reveal rapid deglaciation between ~8 and ~7 ka. After ~7 ka, the ice margin continued to retreat inland behind its present position. Although it is difficult to reconstruct how far inland the ice margin retreated, the Little Ice Age advance reworked marine bivalves that date from 2.2 to 6.1 ka (Weidick and Bennike, 2007). The bivalve ages indicate that the ice margin was behind its Little Ice Age position between ~6 and ~2 ka, and that its Neoglacial advance post-dates ~2 ka. We improve the timing of the Neoglacial advance of Jakobshavn Isbrae by collecting sediment cores from lakes that are beyond the Little Ice Age margin but close enough to receive ice sheet meltwater during the Little Ice Age advance. The sediments in these "threshold" lakes contain distinct units of varved sediments (representing a proglacial environment) that sharply overlie gyttja (representing a non-glacial environment). Four radiocarbon ages of the sedimentary contacts from three different lake sites range from 530±10 to 370±60 cal yr BP (1410-1640 AD), and reveal when Jakobshavn Isbrae neared its maximum Little Ice Age margin. Furthermore, the lake sediments reveal that between early Holocene deglaciation and the Little Ice Age, Jakobshavn Isbrae never spilled into these lake basins, indicating that the Little Ice Age was the most extensive position of this sector of the Greenland Ice Sheet since deglaciation. Future work will be focused on generating climate reconstructions from lake sediments and microfossils (chironomids), and subsequently drawing links between past climate change and corresponding glacier response.
We present a new approach to derive control information from ICESat data that enables rigorous re... more We present a new approach to derive control information from ICESat data that enables rigorous registration of aerial and satellite imagery. The technique, based on matching terrain features identified from ICESat measurements and aerial imagery, opens the door to transform results of previous studies to a global reference frame. We demonstrate the proposed methodology with historical aerial photographs to determine surface changes between 1979 and 2004 over Byrd Glacier. This is important because there is no satellite radar altimetry coverage south of 81.5° S, which limits mass balance knowledge of outlet glaciers draining the East Antarctic ice sheet through the southern Transantarctic Mountains. Our study indicates that the grounded part of Byrd Glacier is close to being in balance. However, we observe large thinning on the floating part of the glacier, probably induced by increased basal melting.
Digital elevation models are essential tools in many glaciological studies and especially for mas... more Digital elevation models are essential tools in many glaciological studies and especially for mass balance studies, structural geology modeling and advance remote sensing and geophysical processing. However, due to the hostile climate and inaccessible environment of the Antarctic continent, there are insufficient elevation databases and their quality is poor. In this paper, we analysis the spatial distribution of error in the different DEMs that exists at the Antarctica Transantarctic Mountains. Based on this analysis, we investigate the various methods to combine elevation models with different properties (resolution, horizontal and vertical accuracy). There are five major data sets in the project area: The USGS 1:50000 maps which, covers the north west part of the project area and have 50 meter contour line interval; USGS 1:250000, taken from the Antarctic Digital Database, which, covers all our project area and have 200 meter contour line interval; satellite radar altimetry data derived from ERS-1 with 5 km resolution; airborne Radio-Echo Sounding profile data at the north east part of the project collected by Scott Polar Research Institute and field surveying control points collected by USGS. Our final goal was to compile all those elevation models into one uniform grid elevation model with the highest accuracy and resolution that can be obtained. Many techniques and algorithm's exists for integrating database, some are based on interpolation methods in the boundary zone, other techniques perform simple data merging and apply various filtering functions to make the transition smoother. We review those procedures and compare their properties and apply some of them in our study. Last, we propose a method to combine the different DEM into one set using universal Kriging concept. In this process, we compute a covariance matrix for every data set individually and a cross covariance of the individual data set in the predication computation.
Epic3science in China Series D Earth Sciences 50 Pp 1693 1706 Isbn 1006 9313 18, 2007
Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a −1 and 2.1±2.4 ... more Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a −1 and 2.1±2.4 Gt a −1 , respectively, while the Fisher Glacier is approximately in balance. The upstream region as a whole has a positive imbalance of 5.9±4.9 Gt a −1 . The three same glaciers downstream of the ANARE LGB traverse line are in negative imbalance, where the whole downstream region has a negative imbalance of −8.5±5.8 Gt a −1 . Overall the mass budgets of the Lambert, Mellor, and Fisher Glaciers are close to balance, and the collective three-glacier system is also nearly in balance with a mass budget of −2.6±6.5 Gt a −1 . The significant positive imbalances for the interior basin upstream of the ice-movement stations established in the early 1970s (GL line) reported previously are possibly due to an overestimate of the total accumulation and an underestimate of the ice flux through the GL line.
Ieee Transactions on Geoscience and Remote Sensing, Nov 1, 2010
We present a technique for automatically labeling segmented hyperspectral imagery with semantical... more We present a technique for automatically labeling segmented hyperspectral imagery with semantically meaningful material labels. The technique compares the mean signatures of each image segment to a spectral library of known materials, and material labels are assigned to image segments according to the most similar library entry. The similarity between spectral signatures is evaluated using our recently proposed CICR d similarity measure designed specifically for hyperspectral imagery. This measure considers both the continuum-intact reflectance spectrum and its continuum-removed representation. We provide a thorough assessment of this measure by comparison to several commonly used similarity measures on a well-studied lowaltitude Airborne Visible/Infrared Imaging Spectrometer image of an urban area. We evaluate our results using both information-theoretic techniques and visual validation of the resulting spectral matches.
The Greenland Ice Sheet (GIS) plays a critical role in the cryosphere's link with climate ch... more The Greenland Ice Sheet (GIS) plays a critical role in the cryosphere's link with climate change. The recent fluctuations of thickness and velocity of Jakobshavn Isbræ, one of the largest outlet glaciers draining the GIS, indicates that Greenland's outlet glaciers have the potential to make faster contributions to sea-level rise than previously believed. To evaluate whether ongoing changes in ice flow are climatically significant, ice stream histories must be determined over longer timescales. Although the 35 km retreat of Jakobshavn Isbræ's calving front since the Little Ice Age (LIA) maximum extent (1850 AD) is well documented, it is does not represent the history of the broader ice margin because the terminus was periodically floating and thus susceptible to subtle perturbations in climate and ocean conditions. Here, we combine a D reconstruction of margin retreat from the LIA extent, measured from stereo imagery, with a geologic reconstruction of the timing and magnitude of the advance phase of the ice margin during LIA, to quantify the response of broader Jakobshavn Isbræ ice margin to LIA climate change. We measured the ice sheet margin in 3D from vegetation trimlines marking the LIA ice extent (1850 AD), aerial photographs acquired in 1985, and SPOT satellite images acquired in 2007. The calving front of Jakobshavn Isbræ retreated at an average rate of 0.178 km/yr between the LIA and 1985 (over which time mean annual temperature increased by 2.76°C). The average retreat rate increased to 0.545 km/yr between 1985 and 2007 (mean annual temperature increased 0.23°C). Land based margins north of Jakobshavn Isbræ retreated at an average rate of 0.007 km/yr between 1850 and 1985, and increased to 0.030 km/yr between 1985 and 2007. Alanngorliup Sermia, an outlet glacier ~30 km south of Jakobshavn Isbræ, experienced negligible change between 1850 and 1985, and retreated at an average rate of 0.017 km/yr between 1985 and 2007. We place these post-1850 AD ice margin changes into a longer-term context using sedimentary signatures stored in proglacial threshold lakes. Radiocarbon-dated sediment sequences from three lakes reveal that the land-based ice margin north of Jakobshavn Isbræ has resided near its 1850 extent since 1400-1640 AD. Data from one lake south of Jakobshavn Isbræ suggest that the ice margin has been near its 1850 margin for ~2000 years. Together, these data reveal that the Jakobshavn ice margin responds to climate change on centennial timescales, but varying rates of retreat since 1850 AD highlight the modulation of retreat by dynamic controls. Furthermore, on centennial timescales, the marine terminus of Jakobshavn Isbræ seems to have a significantly larger response than adjacent land-based margins to equal climate forcing.
2011 3rd Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2011
Hyperspectral imagery provides ample signal content to identify and distinguish between spectrall... more Hyperspectral imagery provides ample signal content to identify and distinguish between spectrally similar, but compositionally unique, materials, but representative training samples for all materials in a given scene are often unavailable in remote sensing applications. We propose a technique which leverages training spectra of materials from one hyperspectral image (the source), for classifying another (target) hyperspectral image, allowing class discovery in the absence of representative training samples for some classes in the target image. By locating spectra of known material species in the source image which are also known in the target image, we derive a transformation that compensates for systematic spectral differences between the images, including atmospheric or seasonal effects, calibration differences, and noise. With this transformation -applied as a similarity measure -we can adapt a classifier trained on spectra from the source image, to classify the target image. We evaluate our technique between a pair of synthetic hyperspectral images with systematic differences in the spectral signatures of corresponding materials. Then we assess the feasibility of using synthetic imagery for training a classifier to identify spectral species in similar, real images, and show knowledge transfer results between a synthetic (HYDICE-type) source image and a real low-altitude AVIRIS target image of a complex urban area.
The mass balance of ice in Antarctica is a prime need in science. The ice sheets are major variab... more The mass balance of ice in Antarctica is a prime need in science. The ice sheets are major variables in the global budget that controls sea level. It could be that thinning of the ice sheets accounts for the current rate of rise of sea level. There is a limited suite of techniques available for measuring mass-balance in Antarctica. A report is presented on the first of intended repeat surface mapping from an aircraft with GPS position determination and a downward-looking laser ranger. This method has the great merit of being precise and of covering large regions. Moreover, laser flights are used to make topographic maps and describe the shape of unusual portions of the ice sheet. The detection of special surface features raises the possibility of some mechanical understanding of ice sheet change.
Researchers of NASA's GSFC are currently developing a scanning airborne photon-counting laser... more Researchers of NASA's GSFC are currently developing a scanning airborne photon-counting laser altimeter. This paper summarizes the creation of high resolution, precise DEMs from repeat passes of airborne laser scanning surveys to validate this new system. To study coastal erosion several sections of the Atlantic and Pacific coast have been mapped by NASA's Airborne Topographic Mapper (ATM) conical scanning altimeter.
22nd Digital Avionics Systems Conference. Proceedings (Cat. No.03CH37449), 2003
This paper is concerned with fusing aerial imagery, LIDAR point clouds, and hyperspectral imagery... more This paper is concerned with fusing aerial imagery, LIDAR point clouds, and hyperspectral imagery for the purpose of automated urban mapping. Instead of performing traditional supervised and unsupervised classification of hyperspectral data we propose a region growing approach from seed pixels that originate from fusing LIDAR and aerial imagery. This requires a thorough alignment of all sensors involved-a problem that is solved with sensor invariant features. The common system is the geodetic reference frame in which the LIDAR points are computed. The alignment results in transformations from sensor space to object space and back, avoiding resampling the sensor data. After describing the major aspects, an example demonstrates the feasibility of the proposed fusion approach.
The major factors affecting the accuracy of Airborne Laser Scanning (ALS) systems are the errors ... more The major factors affecting the accuracy of Airborne Laser Scanning (ALS) systems are the errors in ranging, in the position of the laser firing point, and in the attitude of the laser beam. Since the derivation of a precise theoretical accuracy model is rather complicated, accuracy estimates are mostly obtained by comparing Digital Elevation Models (DEMs) derived from laser scanning
The Transantarctic Mountains (TAM) rift flank uplift has developed along the ancestral margin of ... more The Transantarctic Mountains (TAM) rift flank uplift has developed along the ancestral margin of the East Antarctic craton, rimming the thinned lithosphere of the West Antarctic rift system. The extensive ice cover hampers regional mapping of faults and other geologic boundaries, hence the large-scale configuration of structural boundaries remains poorly defined. TAMARA is a collaborative research program designed to document the regional structural and magmatic architecture of the TAM in southern Victoria Land (SVL). Aeromagnetic data have been acquired in a cooperative U.S.-German field campaign by a helicopter-borne semi-draped survey. As part of the TAMARA program a GIS database of satellite imagery and geological and geophysical data sets has been developed to support modeling and interpretation of the magnetic data and for long-term study of the evolution of the TAM. Regional structural maps from satellite imagery and aeromagnetic data are used to test models for the structura...
Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with to... more Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades. On average, the region has been in balance, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the ice sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.
Planned to launch in 2015, ICEsat-2 will measure changes in polar ice coverage and estimate chang... more Planned to launch in 2015, ICEsat-2 will measure changes in polar ice coverage and estimate changes in the Earth's bio-mass by measuring vegetation canopy height.
Journal of Volcanology and Geothermal Research, 2008
The lidar observations reported here have provided the first high precision topographic data on t... more The lidar observations reported here have provided the first high precision topographic data on the active craters of Erebus volcano, Antarctica. Digital elevation data are invaluable for geomorphic analysis of volcanoes especially when combined with methods to automatically extract landscape features. The data are indispensable for studying eruptive events and volcano-tectonic processes. Airborne laser scanning or lidar is a rapidly emerging technology to map surface topography with high accuracy and detail, comparable to a 1:1000 scale map. In the austral summer of 2001-2002 airborne laser scanning data were collected in Antarctica over the summit plateau of Erebus volcano. We describe the high-resolution data set from Erebus, products derived from the data and demonstrate how extracted topographic features can be used in the geomorphic analysis of volcanoes. Background is presented on the airborne laser scanning method and on the accuracy estimation of laser points. We describe the computation of a high-resolution DEM with a grid size of 2 m × 2 m for the summit area of Erebus volcano. Errors in the DEM are assessed using independent ground-based GPS data and the RMS error is estimated to be ±0.39 m. Visualization methods reveal topographic features that are very useful for geomorphic analysis. Automatic feature extraction and processing is necessary to exploit the high-resolution and accurate elevation data. Methods are described to extract 1D and 2D features and organize them for subsequent analysis. Fitting analytical functions to 3D point clouds or DEMs is particularly effective in extracting topographic features, including planes, higher order surfaces, cones, and conic sections. These methods are used to obtain a quantitative description of the calderas and modern-day crater of Erebus. Especially valuable are the measured surface areas if the lava lakes as these control thermal emissions and gas fluxes from the volcano. Examination of the surface elevations of Ray Lava Lake, Werner Vent and Active Vent indicates that the active vents were more or less in magmastatic equilibrium in 2001 December. Conic segments are fitted to mapped sections of caldera rims to identify the sections buried under younger lava flows or covered by ice and snow. Automatic methods are used to detect and characterize lava channels using geomorphometric maps generated from the DEM.
The Greenland Ice Sheet is undergoing dramatic change. How the ice sheet continues to respond to ... more The Greenland Ice Sheet is undergoing dramatic change. How the ice sheet continues to respond to climate change has important ramifications for global climate and sea level rise, but the observation-based record of ice sheet change is extremely short. We use glacial-geologic techniques to determine the behavior of the Greenland Ice Sheet over longer timescales. In particular, we focus on the Holocene history of Jakobshavn Isbrae, one of the key ice streams on Greenland that is responsible for disproportionate mass loss of the Greenland Ice Sheet. Radiocarbon ages from basal lake sediments and 10Be exposure ages of bedrock spanning from the present ice margin to Disko Bugt, ~50 km west, reveal rapid deglaciation between ~8 and ~7 ka. After ~7 ka, the ice margin continued to retreat inland behind its present position. Although it is difficult to reconstruct how far inland the ice margin retreated, the Little Ice Age advance reworked marine bivalves that date from 2.2 to 6.1 ka (Weidick and Bennike, 2007). The bivalve ages indicate that the ice margin was behind its Little Ice Age position between ~6 and ~2 ka, and that its Neoglacial advance post-dates ~2 ka. We improve the timing of the Neoglacial advance of Jakobshavn Isbrae by collecting sediment cores from lakes that are beyond the Little Ice Age margin but close enough to receive ice sheet meltwater during the Little Ice Age advance. The sediments in these "threshold" lakes contain distinct units of varved sediments (representing a proglacial environment) that sharply overlie gyttja (representing a non-glacial environment). Four radiocarbon ages of the sedimentary contacts from three different lake sites range from 530±10 to 370±60 cal yr BP (1410-1640 AD), and reveal when Jakobshavn Isbrae neared its maximum Little Ice Age margin. Furthermore, the lake sediments reveal that between early Holocene deglaciation and the Little Ice Age, Jakobshavn Isbrae never spilled into these lake basins, indicating that the Little Ice Age was the most extensive position of this sector of the Greenland Ice Sheet since deglaciation. Future work will be focused on generating climate reconstructions from lake sediments and microfossils (chironomids), and subsequently drawing links between past climate change and corresponding glacier response.
We present a new approach to derive control information from ICESat data that enables rigorous re... more We present a new approach to derive control information from ICESat data that enables rigorous registration of aerial and satellite imagery. The technique, based on matching terrain features identified from ICESat measurements and aerial imagery, opens the door to transform results of previous studies to a global reference frame. We demonstrate the proposed methodology with historical aerial photographs to determine surface changes between 1979 and 2004 over Byrd Glacier. This is important because there is no satellite radar altimetry coverage south of 81.5° S, which limits mass balance knowledge of outlet glaciers draining the East Antarctic ice sheet through the southern Transantarctic Mountains. Our study indicates that the grounded part of Byrd Glacier is close to being in balance. However, we observe large thinning on the floating part of the glacier, probably induced by increased basal melting.
Digital elevation models are essential tools in many glaciological studies and especially for mas... more Digital elevation models are essential tools in many glaciological studies and especially for mass balance studies, structural geology modeling and advance remote sensing and geophysical processing. However, due to the hostile climate and inaccessible environment of the Antarctic continent, there are insufficient elevation databases and their quality is poor. In this paper, we analysis the spatial distribution of error in the different DEMs that exists at the Antarctica Transantarctic Mountains. Based on this analysis, we investigate the various methods to combine elevation models with different properties (resolution, horizontal and vertical accuracy). There are five major data sets in the project area: The USGS 1:50000 maps which, covers the north west part of the project area and have 50 meter contour line interval; USGS 1:250000, taken from the Antarctic Digital Database, which, covers all our project area and have 200 meter contour line interval; satellite radar altimetry data derived from ERS-1 with 5 km resolution; airborne Radio-Echo Sounding profile data at the north east part of the project collected by Scott Polar Research Institute and field surveying control points collected by USGS. Our final goal was to compile all those elevation models into one uniform grid elevation model with the highest accuracy and resolution that can be obtained. Many techniques and algorithm's exists for integrating database, some are based on interpolation methods in the boundary zone, other techniques perform simple data merging and apply various filtering functions to make the transition smoother. We review those procedures and compare their properties and apply some of them in our study. Last, we propose a method to combine the different DEM into one set using universal Kriging concept. In this process, we compute a covariance matrix for every data set individually and a cross covariance of the individual data set in the predication computation.
Epic3science in China Series D Earth Sciences 50 Pp 1693 1706 Isbn 1006 9313 18, 2007
Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a −1 and 2.1±2.4 ... more Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a −1 and 2.1±2.4 Gt a −1 , respectively, while the Fisher Glacier is approximately in balance. The upstream region as a whole has a positive imbalance of 5.9±4.9 Gt a −1 . The three same glaciers downstream of the ANARE LGB traverse line are in negative imbalance, where the whole downstream region has a negative imbalance of −8.5±5.8 Gt a −1 . Overall the mass budgets of the Lambert, Mellor, and Fisher Glaciers are close to balance, and the collective three-glacier system is also nearly in balance with a mass budget of −2.6±6.5 Gt a −1 . The significant positive imbalances for the interior basin upstream of the ice-movement stations established in the early 1970s (GL line) reported previously are possibly due to an overestimate of the total accumulation and an underestimate of the ice flux through the GL line.
Ieee Transactions on Geoscience and Remote Sensing, Nov 1, 2010
We present a technique for automatically labeling segmented hyperspectral imagery with semantical... more We present a technique for automatically labeling segmented hyperspectral imagery with semantically meaningful material labels. The technique compares the mean signatures of each image segment to a spectral library of known materials, and material labels are assigned to image segments according to the most similar library entry. The similarity between spectral signatures is evaluated using our recently proposed CICR d similarity measure designed specifically for hyperspectral imagery. This measure considers both the continuum-intact reflectance spectrum and its continuum-removed representation. We provide a thorough assessment of this measure by comparison to several commonly used similarity measures on a well-studied lowaltitude Airborne Visible/Infrared Imaging Spectrometer image of an urban area. We evaluate our results using both information-theoretic techniques and visual validation of the resulting spectral matches.
The Greenland Ice Sheet (GIS) plays a critical role in the cryosphere's link with climate ch... more The Greenland Ice Sheet (GIS) plays a critical role in the cryosphere's link with climate change. The recent fluctuations of thickness and velocity of Jakobshavn Isbræ, one of the largest outlet glaciers draining the GIS, indicates that Greenland's outlet glaciers have the potential to make faster contributions to sea-level rise than previously believed. To evaluate whether ongoing changes in ice flow are climatically significant, ice stream histories must be determined over longer timescales. Although the 35 km retreat of Jakobshavn Isbræ's calving front since the Little Ice Age (LIA) maximum extent (1850 AD) is well documented, it is does not represent the history of the broader ice margin because the terminus was periodically floating and thus susceptible to subtle perturbations in climate and ocean conditions. Here, we combine a D reconstruction of margin retreat from the LIA extent, measured from stereo imagery, with a geologic reconstruction of the timing and magnitude of the advance phase of the ice margin during LIA, to quantify the response of broader Jakobshavn Isbræ ice margin to LIA climate change. We measured the ice sheet margin in 3D from vegetation trimlines marking the LIA ice extent (1850 AD), aerial photographs acquired in 1985, and SPOT satellite images acquired in 2007. The calving front of Jakobshavn Isbræ retreated at an average rate of 0.178 km/yr between the LIA and 1985 (over which time mean annual temperature increased by 2.76°C). The average retreat rate increased to 0.545 km/yr between 1985 and 2007 (mean annual temperature increased 0.23°C). Land based margins north of Jakobshavn Isbræ retreated at an average rate of 0.007 km/yr between 1850 and 1985, and increased to 0.030 km/yr between 1985 and 2007. Alanngorliup Sermia, an outlet glacier ~30 km south of Jakobshavn Isbræ, experienced negligible change between 1850 and 1985, and retreated at an average rate of 0.017 km/yr between 1985 and 2007. We place these post-1850 AD ice margin changes into a longer-term context using sedimentary signatures stored in proglacial threshold lakes. Radiocarbon-dated sediment sequences from three lakes reveal that the land-based ice margin north of Jakobshavn Isbræ has resided near its 1850 extent since 1400-1640 AD. Data from one lake south of Jakobshavn Isbræ suggest that the ice margin has been near its 1850 margin for ~2000 years. Together, these data reveal that the Jakobshavn ice margin responds to climate change on centennial timescales, but varying rates of retreat since 1850 AD highlight the modulation of retreat by dynamic controls. Furthermore, on centennial timescales, the marine terminus of Jakobshavn Isbræ seems to have a significantly larger response than adjacent land-based margins to equal climate forcing.
2011 3rd Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2011
Hyperspectral imagery provides ample signal content to identify and distinguish between spectrall... more Hyperspectral imagery provides ample signal content to identify and distinguish between spectrally similar, but compositionally unique, materials, but representative training samples for all materials in a given scene are often unavailable in remote sensing applications. We propose a technique which leverages training spectra of materials from one hyperspectral image (the source), for classifying another (target) hyperspectral image, allowing class discovery in the absence of representative training samples for some classes in the target image. By locating spectra of known material species in the source image which are also known in the target image, we derive a transformation that compensates for systematic spectral differences between the images, including atmospheric or seasonal effects, calibration differences, and noise. With this transformation -applied as a similarity measure -we can adapt a classifier trained on spectra from the source image, to classify the target image. We evaluate our technique between a pair of synthetic hyperspectral images with systematic differences in the spectral signatures of corresponding materials. Then we assess the feasibility of using synthetic imagery for training a classifier to identify spectral species in similar, real images, and show knowledge transfer results between a synthetic (HYDICE-type) source image and a real low-altitude AVIRIS target image of a complex urban area.
The mass balance of ice in Antarctica is a prime need in science. The ice sheets are major variab... more The mass balance of ice in Antarctica is a prime need in science. The ice sheets are major variables in the global budget that controls sea level. It could be that thinning of the ice sheets accounts for the current rate of rise of sea level. There is a limited suite of techniques available for measuring mass-balance in Antarctica. A report is presented on the first of intended repeat surface mapping from an aircraft with GPS position determination and a downward-looking laser ranger. This method has the great merit of being precise and of covering large regions. Moreover, laser flights are used to make topographic maps and describe the shape of unusual portions of the ice sheet. The detection of special surface features raises the possibility of some mechanical understanding of ice sheet change.
Researchers of NASA's GSFC are currently developing a scanning airborne photon-counting laser... more Researchers of NASA's GSFC are currently developing a scanning airborne photon-counting laser altimeter. This paper summarizes the creation of high resolution, precise DEMs from repeat passes of airborne laser scanning surveys to validate this new system. To study coastal erosion several sections of the Atlantic and Pacific coast have been mapped by NASA's Airborne Topographic Mapper (ATM) conical scanning altimeter.
22nd Digital Avionics Systems Conference. Proceedings (Cat. No.03CH37449), 2003
This paper is concerned with fusing aerial imagery, LIDAR point clouds, and hyperspectral imagery... more This paper is concerned with fusing aerial imagery, LIDAR point clouds, and hyperspectral imagery for the purpose of automated urban mapping. Instead of performing traditional supervised and unsupervised classification of hyperspectral data we propose a region growing approach from seed pixels that originate from fusing LIDAR and aerial imagery. This requires a thorough alignment of all sensors involved-a problem that is solved with sensor invariant features. The common system is the geodetic reference frame in which the LIDAR points are computed. The alignment results in transformations from sensor space to object space and back, avoiding resampling the sensor data. After describing the major aspects, an example demonstrates the feasibility of the proposed fusion approach.
The major factors affecting the accuracy of Airborne Laser Scanning (ALS) systems are the errors ... more The major factors affecting the accuracy of Airborne Laser Scanning (ALS) systems are the errors in ranging, in the position of the laser firing point, and in the attitude of the laser beam. Since the derivation of a precise theoretical accuracy model is rather complicated, accuracy estimates are mostly obtained by comparing Digital Elevation Models (DEMs) derived from laser scanning
The Transantarctic Mountains (TAM) rift flank uplift has developed along the ancestral margin of ... more The Transantarctic Mountains (TAM) rift flank uplift has developed along the ancestral margin of the East Antarctic craton, rimming the thinned lithosphere of the West Antarctic rift system. The extensive ice cover hampers regional mapping of faults and other geologic boundaries, hence the large-scale configuration of structural boundaries remains poorly defined. TAMARA is a collaborative research program designed to document the regional structural and magmatic architecture of the TAM in southern Victoria Land (SVL). Aeromagnetic data have been acquired in a cooperative U.S.-German field campaign by a helicopter-borne semi-draped survey. As part of the TAMARA program a GIS database of satellite imagery and geological and geophysical data sets has been developed to support modeling and interpretation of the magnetic data and for long-term study of the evolution of the TAM. Regional structural maps from satellite imagery and aeromagnetic data are used to test models for the structura...
Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with to... more Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades. On average, the region has been in balance, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the ice sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.
Planned to launch in 2015, ICEsat-2 will measure changes in polar ice coverage and estimate chang... more Planned to launch in 2015, ICEsat-2 will measure changes in polar ice coverage and estimate changes in the Earth's bio-mass by measuring vegetation canopy height.
Journal of Volcanology and Geothermal Research, 2008
The lidar observations reported here have provided the first high precision topographic data on t... more The lidar observations reported here have provided the first high precision topographic data on the active craters of Erebus volcano, Antarctica. Digital elevation data are invaluable for geomorphic analysis of volcanoes especially when combined with methods to automatically extract landscape features. The data are indispensable for studying eruptive events and volcano-tectonic processes. Airborne laser scanning or lidar is a rapidly emerging technology to map surface topography with high accuracy and detail, comparable to a 1:1000 scale map. In the austral summer of 2001-2002 airborne laser scanning data were collected in Antarctica over the summit plateau of Erebus volcano. We describe the high-resolution data set from Erebus, products derived from the data and demonstrate how extracted topographic features can be used in the geomorphic analysis of volcanoes. Background is presented on the airborne laser scanning method and on the accuracy estimation of laser points. We describe the computation of a high-resolution DEM with a grid size of 2 m × 2 m for the summit area of Erebus volcano. Errors in the DEM are assessed using independent ground-based GPS data and the RMS error is estimated to be ±0.39 m. Visualization methods reveal topographic features that are very useful for geomorphic analysis. Automatic feature extraction and processing is necessary to exploit the high-resolution and accurate elevation data. Methods are described to extract 1D and 2D features and organize them for subsequent analysis. Fitting analytical functions to 3D point clouds or DEMs is particularly effective in extracting topographic features, including planes, higher order surfaces, cones, and conic sections. These methods are used to obtain a quantitative description of the calderas and modern-day crater of Erebus. Especially valuable are the measured surface areas if the lava lakes as these control thermal emissions and gas fluxes from the volcano. Examination of the surface elevations of Ray Lava Lake, Werner Vent and Active Vent indicates that the active vents were more or less in magmastatic equilibrium in 2001 December. Conic segments are fitted to mapped sections of caldera rims to identify the sections buried under younger lava flows or covered by ice and snow. Automatic methods are used to detect and characterize lava channels using geomorphometric maps generated from the DEM.
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Papers by Bea Csatho