1,407 research outputs found
The significance of the Skylab altimeter experiment results and potential applications
The Skylab Altimeter Experiment has proven the capability of the altimeter for measurement of sea surface topography. The geometric determination of the geoid/mean sea level from satellite altimetry is a new approach having significant applications in many disciplines including geodesy and oceanography. A Generalized Least Squares Collocation Technique was developed for determination of the geoid from altimetry data. The technique solves for the altimetry geoid and determines one bias term for the combined effect of sea state, orbit, tides, geoid, and instrument error using sparse ground truth data. The influence of errors in orbit and a priori geoid values are discussed. Although the Skylab altimeter instrument accuracy is about + or - 1 m, significant results were obtained in identification of large geoidal features such as over the Puerto Rico trench. Comparison of the results of several passes shows that good agreement exists between the general slopes of the altimeter geoid and the ground truth, and that the altimeter appears to be capable of providing more details than are now available with best known geoids. The altimetry geoidal profiles show excellent correlations with bathymetry and gravity. Potential applications of altimetry results to geodesy, oceanography, and geophysics are discussed
Calibration and evaluation of Skylab altimetry for geodetic determination of the geoid
There are no author-identified significant results in this report
Deformed Complex Hermite Polynomials
We study a class of bivariate deformed Hermite polynomials and some of their
properties using classical analytic techniques and the Wigner map. We also
prove the positivity of certain determinants formed by the deformed
polynomials. Along the way we also work out some additional properties of the
(undeformed) complex Hermite polynomials and their relationships to the
standard Hermite polynomials (of a single real variable).Comment: 12 page
The application of Skylab altimetry to marine geoid determination
The author had identified the following significant results. The major results can be divided broadly into two groups. One group is concerned with the effects of errors inherent in the various input data, such as the orbit emphemeris, a priori geoid etc. The other consists of the results of the actual analysis of the data from the Skylab EREP passes 4, 6, 7, and 9. Results from the first group were obtained from the analysis of some preliminary data from EREP pass 9 mode 5. The second group of results consists of a set of recovered bias terms for each of the submodes of observations and a set of nine altimetry geoid profiles corresponding to the various passes and modes. Along with each of these profiles, the a priori geoid, gravity anomaly, and the bathymetric data profiles are also presented for easy comparison
Calibration and evaluation of Skylab altimetry for geodetic determination of the geoid
There are no author-identified significant results in this report
Improved ground truth geoid for the GEOS-3 calibration area
The purpose of this investigation is to develop methods and procedures are reported for computing a detailed geoid to be used as geodetic ground truth for the calibration and verification of GEOS-3 altimeter data. The technique developed is based on rectifying the best available detailed geoid so that the rectified geoid will have correct scale, orientation, shape and position with respect to the geocenter. The approach involved the development of a mathematical model based on a second degree polynomial, in rectangular Cartesian coordinates, describing the geoid undulations at the control stations. A generalized least squares solution was obtained for the polynomial which describes the variation of the undulation differences between the control stations geoid and the gravimetric geoid. Three rectified geoid were determined. These geoids correspond to three sets of tracking station data: (1) WFC/C-band data; (2) GSFC/C-band data; and (3) OSU-275 data. The absolute accuracy of these rectified geoids is linearly correlated with the uncertainties of the tracking station coordinates and, to a certain extent, with those of the detailed geoid being rectified
Calibration and evaluation of Skylab altimetry for geodetic determination of the geoid
The author has identified the following significant results. The Skylab altimeter experiment has proven the capability of the altimeter for measurement of sea surface topography. The geometric determination of the geoid/mean sea level from satellite altimetry is a new approach having significant applications in many disciplines including geodesy and oceanography. A generalized least squares collocation technique was developed for determination of the geoid from altimetry data. The technique solves for the altimetry geoid and determines one bias term for the combined effect of sea state, orbit, tides, geoid, and instrument error using sparse ground truth data. The influence of errors in orbit and a priori geoid values are discussed. Although the Skylab altimeter instrument accuracy is about plus or minus 1m, significant results were obtained in identification of large geoidal features such as over the Puerto Rico trench. Comparison of the results of several passes shows that good agreement exists between the general slopes of the altimeter geoid and the ground truth, and that the altimeter appears to be capable of providing more details than are now available with best known geoids
Automated image processing for quantification of blue-stain discolouration of Norway spruce wood
Bioincising is a promising method for enhancing liquid uptake (e.g. preservatives or wood-modification agents) in refractory wood. Incubation with the white-rot fungus, Physisporinus vitreus, which selectively degrades pit membranes, results in deeper and more homogeneous penetration of liquids. Conventional methods of assessing the degree of fungal discolouration of wood after treatment with preservatives (e.g. European standard EN 152) are partly based on a subjective rating scale, which gives a rough value of the surface colonisation by blue-stain fungi. Hence, an automated image processing (AIP) procedure was developed for standardised quantification of the segmentation thresholds of discolouration and tested against manual segmentation analysis. Using the red filter in the AIP method revealed high correlation (R 2 0.95) and allowed for more user friendly and objective determination of blue staining of woo
The SO(N) principal chiral field on a half-line
We investigate the integrability of the SO(N) principal chiral model on a
half-line, and find that mixed Dirichlet/Neumann boundary conditions (as well
as pure Dirichlet or Neumann) lead to infinitely many conserved charges
classically in involution. We use an anomaly-counting method to show that at
least one non-trivial example survives quantization, compare our results with
the proposed reflection matrices, and, based on these, make some preliminary
remarks about expected boundary bound-states.Comment: 7 pages, Late
Almost commutative Riemannian geometry: wave operators
Associated to any (pseudo)-Riemannian manifold of dimension is an
-dimensional noncommutative differential structure (\Omega^1,\extd) on
the manifold, with the extra dimension encoding the classical Laplacian as a
noncommutative `vector field'. We use the classical connection, Ricci tensor
and Hodge Laplacian to construct (\Omega^2,\extd) and a natural
noncommutative torsion free connection on . We show
that its generalised braiding \sigma:\Omega^1\tens\Omega^1\to
\Omega^1\tens\Omega^1 obeys the quantum Yang-Baxter or braid relations only
when the original is flat, i.e their failure is governed by the Riemann
curvature, and that \sigma^2=\id only when is Einstein. We show that if
has a conformal Killing vector field then the cross product algebra
viewed as a noncommutative analogue of has a
natural -dimensional calculus extending and a natural spacetime
Laplacian now directly defined by the extra dimension. The case
recovers the Majid-Ruegg bicrossproduct flat spacetime model and the
wave-operator used in its variable speed of light preduction, but now as an
example of a general construction. As an application we construct the wave
operator on a noncommutative Schwarzschild black hole and take a first look at
its features. It appears that the infinite classical redshift/time dilation
factor at the event horizon is made finite.Comment: 39 pages, 4 pdf images. Removed previous Sections 5.1-5.2 to a
separate paper (now ArXived) to meet referee length requirements.
Corresponding slight restructure but no change to remaining conten
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