scholarly journals Uncertainty analysis for transverse surface velocity measurements

2020 ◽  
Author(s):  
Jeff W. La Jeunesse ◽  
Peter A. Sable ◽  
John P. Borg
Keyword(s):  
Uncertainty Analysis ◽  
Surface Velocity ◽  
Velocity Measurements

Position Registration of Scanning Lasers for Experimental Spatial Dynamics Modeling

1994 ◽  
Author(s):  
David E. Montgomery ◽  
Robert L. West
Keyword(s):  
Spatial Dynamics ◽  
Spatial Models ◽  
Laser Doppler Vibrometer ◽  
Sample Surface ◽  
Surface Shape ◽  
Surface Velocity ◽  
Multiple Point ◽  
Range Data ◽  
Dynamics Modeling ◽  
Velocity Measurements

Abstract Experimental spatial dynamics modeling involves using scanning lasers to sample surface shape and dynamic response of structures in order to verify structural dynamics design intent. Formation of accurate spatial models from laser-based measurements requires that laser position and orientation be registered relative to a fixed coordinate system. A three point direct registration procedure is defined for shape modeling using laser range and mirror deflection angles. Surface velocity measurements with a portable laser Doppler vibrometer (LDV) also require registration, but range information is unavailable. A multiple point indirect registration algorithm for the LDV is described that involves minimizing three nonlinear equations. A simulated laser rangefinder (LRF) was developed for demonstrating three point direct registration. The 3-D geometry of a compressor housing was modeled by combining range data from multiple laser positions. The multiple point indirect registration was applied to 3-D velocity response field reconstruction of a composite plate from velocity measurements scanned at three separate positions.

Terrain analyses and surface velocity measurements of the Hiorthfjellet rock glacier, Svalbard

2003 ◽  
Vol 14 (4) ◽  
pp. 359-365 ◽  
Author(s):  
Rune S. Ødegård ◽  
Ketil Isaksen ◽  
Trond Eiken ◽  
Johan Ludvig Sollid
Keyword(s):  
Surface Velocity ◽  
Velocity Measurements ◽  
Rock Glacier

scholarly journals Measurement of Surface Strain-Rate on Taku Glacier, Alaska

1964 ◽  
Vol 5 (39) ◽  
pp. 305-313 ◽  
Author(s):  
T. H. Wu ◽  
R. W. Christensen
Keyword(s):  
Strain Rate ◽  
Reasonable Agreement ◽  
Stress Condition ◽  
Surface Strain ◽  
Surface Velocity ◽  
Strain Rates ◽  
Velocity Measurements ◽  
Measured Velocity ◽  
Valley Glacier ◽  
Measured Strain

AbstractStrain-rate and surface velocity measurements were made on a valley glacier. The measured strain-rates were used to calculate the stress condition and velocity distribution in the glacier. The measured velocity is in reasonable agreement with that calculated from Nye’s plasticity solution.

Surface velocity and mass balance of Ice Streams D and E, West Antarctica

1996 ◽  
Vol 42 (142) ◽  
pp. 461-475 ◽  
Author(s):  
Robert Bindschadler ◽  
Patricia Vornberger ◽  
Donald Blankenship ◽  
Ted Scambos ◽  
Robert Jacobel
Keyword(s):  
Mass Balance ◽  
Surface Velocity ◽  
Random Errors ◽  
West Antarctica ◽  
Velocity Measurements ◽  
Ice Streams ◽  
Ice Stream ◽  
Data Density ◽  
Basal Shear ◽  
Collection Methods

AbstractOver 75 000 surface-velocity measurements are extracted from sequential satellite imagery of Ice Streams D and E to reveal a complex pattern of flow not apparent from previous measurements. Horizontal and vertical strain rates, calculated from surface velocity, indicate that the bed experiences larger basal shear where the surface of these ice streams is rougher. Ten airborne-radar profiles and one surface-based radar profile of ice thickness make possible the calculation of mass balance for longitudinal sections of each ice stream. Improved data-collection methods increase data density, substantially reducing random errors in velocity. However, systematic errors continue to limit the ability of the flux-differencing technique used here to resolve local variations in mass balance. Nevertheless, significant local variations in mass balance are revealed, while, overall, Ice Streams D and E are in approximate equilibrium. An earlier estimate of the net mass balance for Ice Stream D is improved.

Inversion of P-SV seismic data

Geophysics ◽  
1986 ◽  
Vol 51 (5) ◽  
pp. 1056-1068 ◽  
Author(s):  
James J. Carazzone
Keyword(s):  
Plane Wave ◽  
Riccati Equation ◽  
Incidence Angle ◽  
Surface Velocity ◽  
Complex Frequency ◽  
Velocity Measurements ◽  
Surface Source ◽  
Matrix Riccati Equation ◽  
Wave Incidence ◽  
Plane Wave Incidence

In a layered elastic material, density, shear velocity, and compressional velocity can be found at any depth from broadband surface measurements at two distinct, nonzero, precritical values of plane‐wave incidence angle. Layer‐stripping inversion uses three‐component surface velocity measurements generated by a polarized surface source to determine subsurface properties incrementally. The surface velocity measurements initialize a first‐order, nonlinear, matrix Riccati equation (derived from the elastic wave equation) which takes advantage of an attractive fixed‐point condition in the complex frequency plane to extract subsurface mechanical impedances. Subsurface density and velocities are recovered from the inverted impedances at two or more plane‐wave incidence angles. General properties of the matrix Riccati equation in the complex frequency plane aid in incorporating bandwidth constraints. Inversion of synthetic plane wave data from a piece‐wise continuous model illustrates inversion effects when only a finite bandwidth is available and when different compressional and shear wavelength distance scales are present.

scholarly journals Recession, thinning, and slowdown of Greenland's Mittivakkat Gletscher

2012 ◽  
Vol 6 (3) ◽  
pp. 2005-2036 ◽  
Author(s):  
S. H. Mernild ◽  
N. T. Knudsen ◽  
J. C. Yde ◽  
M. J. Hoffman ◽  
W. H. Lipscomb ◽  
...  
Keyword(s):  
Deformation Theory ◽  
Peak Velocity ◽  
Satellite Observations ◽  
Surface Velocity ◽  
Ice Thickness ◽  
Velocity Measurements ◽  
The Past ◽  
Ice Surface ◽  
Winter Conditions

Abstract. Glaciers in Southeast Greenland have thinned and receded during the past several decades. Here, we document changes for the Mittivakkat Gletscher, the only glacier in Greenland with long-term mass balance observations and surface velocity measurements (since 1995). Between 1986 and 2011, this glacier shrank by 18 % in surface area, 20 % in mean ice thickness, and 33 % in volume. We attribute these changes to summertime warming and to drier winter conditions. Meanwhile, the annual mean ice surface velocity decreased by 30 %, likely as a dynamic result of thinning. This dynamic thinning is predicted by ice deformation theory but has rarely been observed on decadal time scales. Mittivakkat Gletscher summer surface velocities were on average 50–60 % above winter background values, and up to 160 % higher during peak velocity events. The transition from winter to summer values followed the onset of positive temperatures. Satellite observations show area losses for most other glaciers in the region; these glaciers are likely also to have lost volume (in average around one-third) and slowed down in recent decades.

Prediction of river discharges at confluences based on Entropy theory and surface-velocity measurements

2022 ◽  
pp. 127404
Author(s):  
Farhad Bahmanpouri ◽  
Silvia Barbetta ◽  
Carlo Gualtieri ◽  
Marco Ianniruberto ◽  
Naziano Filizola ◽  
...  
Keyword(s):  
Surface Velocity ◽  
Entropy Theory ◽  
Velocity Measurements
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