320 research outputs found
Calibration and evaluation of Skylab altimetry for geodetic determination of the geoid
There are no author-identified significant results in this report
Calibration and evaluation of Skylab altimetry for geodetic determination of the geoid
There are no author-identified significant results in this report
Applications of satellite and marine geodesy to operations in the ocean environment
The requirements for marine and satellite geodesy technology are assessed with emphasis on the development of marine geodesy. Various programs and missions for identification of the satellite geodesy technology applicable to marine geodesy are analyzed along with national and international marine programs to identify the roles of satellite/marine geodesy techniques for meeting the objectives of the programs and other objectives of national interest effectively. The case for marine geodesy is developed based on the extraction of requirements documented by authoritative technical industrial people, professional geodesists, government agency personnel, and applicable technology reports
Interaction of marine geodesy, satellite technology and ocean physics
The possible applications of satellite technology in marine geodesy and geodetic related ocean physics were investigated. Four major problems were identified in the areas of geodesy and ocean physics: (1) geodetic positioning and control establishment; (2) sea surface topography and geoid determination; (3) geodetic applications to ocean physics; and (4) ground truth establishment. It was found that satellite technology can play a major role in their solution. For solution of the first problem, the use of satellite geodetic techniques, such as Doppler and C-band radar ranging, is demonstrated to fix the three-dimensional coordinates of marine geodetic control if multi-satellite passes are used. The second problem is shown to require the use of satellite altimetry, along with accurate knowledge of ocean-dynamics parameters such as sea state, ocean tides, and mean sea level. The use of both conventional and advanced satellite techniques appeared to be necessary to solve the third and fourth problems
Geodetic analysis of Skylab altimetry preliminary data - SL/2 EREP pass 9
The author has identified the following significant results. The analysis was based on a time series intrinsic relationship between the satellite ephemeris, altimeter measured ranges, and the corresponding a priori values of subsatellite geoidal heights. Using sequential least squares processing with parameter weighting, the objective was to recover (1) the absolute geoidal heights of the subsatellite points, and (2) the associated altimeter calibration constant(s). Preliminary results from Skylab altimetry are given, using various combinations of orbit ephemeris and altimeter ranges as computed differently by NASA/JSC and NASA/Wallops. The influences of orbit accuracy, weighting functions, and a priori ground truth are described, based on the various combination solutions. It is shown that to deduce geoidal height by merely subtracting the height of the satellite from the altimeter range is inadmissible. The results of such direct subtraction can be very misleading if the orbit used is computed from data that included altimeter data used as height constraints. In view of the current state of knowledge, the use of geodetic ground truth samples as control benchmarks appears indispensable for the recovery of absolute geoidal heights with correct scale
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Biometric capture: disrupting the digital codification of black migrants in the UK
The current system of the surveillance of migrants relies on biometric capture. To be captured is to be codified into machine-readable representations. This paper merges technological codifications with political discourse to explore the disproportionate capturing of black migrants in the UK. Using the historical treatment of Nigerian migrants in the UK as an illustration, this paper interrogates how contemporary technologies are used to codify and confine black migrants. This paper explores works from digital artists – Keith Piper and Joy Buolamwini – to address this codification of blackness using biometric technology. It calls for new technological cultures of coding that centre the disruption of violent systems of capture. Failure is defined as this disruption of hegemonic systems of codification and capture that aim to subjugate black communities. This paper stresses that it is only when technologies of capture fail that black and migrant communities can truly experience digital freedom
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
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