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Jon Ove Hagen - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of relative water content in a sub-polar glacier using surface-penetration Radar
    Journal of Glaciology, 1996
    Co-Authors: Svein-erik Hamran, Eldar Aarholt, Jon Ove Hagen
    Abstract:

    Radar-sounding data taken at Uversbreen glacier, Svalbard, are used to estimate the relative water content of the temperate part of the glacier. The relative change in water content is estimated from the strength of the backscattered Radar Energy without knowing the size of the scatterers. The main findings are that the water content is increasing gradually with depth below the cold/temperate interface. The water content is on average changing by a factor of five in the ice, with the exception of some bright spots believed to stem from larger water moulins. The general trend is also that the water content is increasing with lower altitude. The applied technique may be a useful method for large-scale mapping of the relative water-content variation in temperate and polythermal glaciers.

  • Estimation of relative water content in a sub-polar glacier using surface-penetration Radar
    Journal of Glaciology, 1996
    Co-Authors: Svein-erik Hamran, Eldar Aarholt, Jon Ove Hagen
    Abstract:

    AbstractRadar-sounding data taken at Uvérsbreen glacier, Svalbard, are used to estimate the relative water content of the temperate part of the glacier. The relative change in water content of the temperate part of the glacier. The relative change in water content is estimated from the strength of the backscttered Radar Energy without knowing the size of the scatterers. The main findings are that the water content is on average changing by a factor of five in the ice, with the exception of some bright spots believed to stem fro larger water moulins. The general trend is also that the water content is increasing with lower altitude. The applied technique may be a useful method for large-scale mapping of the relative water-content variation in temperate and polythermal glaciers.

Svein-erik Hamran - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of relative water content in a sub-polar glacier using surface-penetration Radar
    Journal of Glaciology, 1996
    Co-Authors: Svein-erik Hamran, Eldar Aarholt, Jon Ove Hagen
    Abstract:

    Radar-sounding data taken at Uversbreen glacier, Svalbard, are used to estimate the relative water content of the temperate part of the glacier. The relative change in water content is estimated from the strength of the backscattered Radar Energy without knowing the size of the scatterers. The main findings are that the water content is increasing gradually with depth below the cold/temperate interface. The water content is on average changing by a factor of five in the ice, with the exception of some bright spots believed to stem from larger water moulins. The general trend is also that the water content is increasing with lower altitude. The applied technique may be a useful method for large-scale mapping of the relative water-content variation in temperate and polythermal glaciers.

  • Estimation of relative water content in a sub-polar glacier using surface-penetration Radar
    Journal of Glaciology, 1996
    Co-Authors: Svein-erik Hamran, Eldar Aarholt, Jon Ove Hagen
    Abstract:

    AbstractRadar-sounding data taken at Uvérsbreen glacier, Svalbard, are used to estimate the relative water content of the temperate part of the glacier. The relative change in water content of the temperate part of the glacier. The relative change in water content is estimated from the strength of the backscttered Radar Energy without knowing the size of the scatterers. The main findings are that the water content is on average changing by a factor of five in the ice, with the exception of some bright spots believed to stem fro larger water moulins. The general trend is also that the water content is increasing with lower altitude. The applied technique may be a useful method for large-scale mapping of the relative water-content variation in temperate and polythermal glaciers.

Wendy Weaver - One of the best experts on this subject based on the ideXlab platform.

  • Ground-penetrating Radar Mappingin Clay:Successfrom South Carolina,USA
    2006
    Co-Authors: Wendy Weaver
    Abstract:

    A ground-penetrating Radar (GPR) survey conducted in a clay-rich floodplain of the Savannah River, South Carolina, producedwhat wereverydifficult tointerpret reflection profiles caused by Energy cou- pling changes. These changes were caused by deep hardened plow furrows at the ground surface that caused antenna movement to beirregular, andEnergy to be transmittedinto the ground at various angles, and with different properties. A dense clay layer also attenuated much of the Radar Energy at about 50 cm, further obscuring the profiles. Despite these ambiguous data, amplitude mapping at slicesbelow the claylayer yieldedimagesofdistinct circularandlinear features, whichprovedtobepa- lisadewallsdatingfromabout thelate Mississippianto Early Contact period (AD1400-1740).Thissurvey illustrates that it is possible to obtain good GPR results even when Energy passes through dense clay and when reflection profiles are obscured by attenuation and coupling changes. Copyright � 2006 JohnWiley & Sons,Ltd.

  • Ground‐penetrating Radar mapping in clay: success from South Carolina, USA
    Archaeological Prospection, 2006
    Co-Authors: Wendy Weaver
    Abstract:

    A ground-penetrating Radar (GPR) survey conducted in a clay-rich floodplain of the Savannah River, South Carolina, produced what were very difficult to interpret reflection profiles caused by Energy coupling changes. These changes were caused by deep hardened plow furrows at the ground surface that caused antenna movement to be irregular, and Energy to be transmitted into the ground at various angles, and with different properties. A dense clay layer also attenuated much of the Radar Energy at about 50 cm, further obscuring the profiles. Despite these ambiguous data, amplitude mapping at slices below the clay layer yielded images of distinct circular and linear features, which proved to be palisade walls dating from about the late Mississippian to Early Contact period (AD1400-1740). This survey illustrates that it is possible to obtain good GPR results even when Energy passes through dense clay and when reflection profiles are obscured by attenuation and coupling changes. Copyright © 2006 John Wiley & Sons, Ltd.

Eldar Aarholt - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of relative water content in a sub-polar glacier using surface-penetration Radar
    Journal of Glaciology, 1996
    Co-Authors: Svein-erik Hamran, Eldar Aarholt, Jon Ove Hagen
    Abstract:

    Radar-sounding data taken at Uversbreen glacier, Svalbard, are used to estimate the relative water content of the temperate part of the glacier. The relative change in water content is estimated from the strength of the backscattered Radar Energy without knowing the size of the scatterers. The main findings are that the water content is increasing gradually with depth below the cold/temperate interface. The water content is on average changing by a factor of five in the ice, with the exception of some bright spots believed to stem from larger water moulins. The general trend is also that the water content is increasing with lower altitude. The applied technique may be a useful method for large-scale mapping of the relative water-content variation in temperate and polythermal glaciers.

  • Estimation of relative water content in a sub-polar glacier using surface-penetration Radar
    Journal of Glaciology, 1996
    Co-Authors: Svein-erik Hamran, Eldar Aarholt, Jon Ove Hagen
    Abstract:

    AbstractRadar-sounding data taken at Uvérsbreen glacier, Svalbard, are used to estimate the relative water content of the temperate part of the glacier. The relative change in water content of the temperate part of the glacier. The relative change in water content is estimated from the strength of the backscttered Radar Energy without knowing the size of the scatterers. The main findings are that the water content is on average changing by a factor of five in the ice, with the exception of some bright spots believed to stem fro larger water moulins. The general trend is also that the water content is increasing with lower altitude. The applied technique may be a useful method for large-scale mapping of the relative water-content variation in temperate and polythermal glaciers.

J. Hebert - One of the best experts on this subject based on the ideXlab platform.

  • MINIMIZING Radar EXPOSURE IN AIR VEHICLE PATH PLANNING
    IFAC Proceedings Volumes, 2002
    Co-Authors: Meir Pachter, J. Hebert
    Abstract:

    Abstract An aircraft exposed to illumination by a tracking Radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory that minimizes the Radar Energy reflected from the target is derived using the Calculus of Variations. The solution is shown to exist only if the angle θf, formed by the lines connecting the Radar to the two prespecified trajectory end points, is less than 60°. In addition, expressions are given for the path length and optimal cost.

  • COOPERATIVE CONTROL OF UAVs
    AIAA Guidance Navigation and Control Conference and Exhibit, 2001
    Co-Authors: J. Hebert, David R. Jacques, Michael Novy, Meir Pachter
    Abstract:

    The cooperative control problem of minimizing the cumulative exposure of UAVs to a tracking Radar is examined. An analytic solution yielding the trajectory that minimizes the Radar Energy reflected from the target has been obtained using the Calculus of Variations.' The analytic results for one aircraft are extended to address cooperative control problems of multiple uninhabited air vehicles versus one Radar. The problem of one aircraft versus multiple Radars is also addressed using a variational approach, as well as a minimax argument. The results are compared to other path planning methods for Radar exposure minimization, specifically the use of Voronoi diagrams.

  • Optimal aircraft trajectories for Radar exposure minimization
    Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148), 2001
    Co-Authors: Meir Pachter, J. Hebert
    Abstract:

    An aircraft exposed to illumination by a tracking Radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory that minimizes the Radar Energy reflected from the target is derived using the calculus of variations. The solution is shown to exist only if the angle /spl theta//sub f/, formed by the lines connecting the Radar to the two prespecified trajectory end points, is less than 60/spl deg/. In addition, expressions are given for the path length and optimal cost.