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  • GEOPHYSICS  (22)
  • EARTH RESOURCES AND REMOTE SENSING  (3)
  • Key words. Robust fitting  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Robust estimation of systematic errors of satellite laser range (1999)
    Springer
    Journal of geodesy 73 (1999), S. 345-349 
    Details
    ISSN: 1432-1394
    Keywords: Key words. Robust fitting ; Systematic errors ; SLR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. Methods for analyzing laser-ranging residuals to estimate station-dependent systematic errors and to eliminate outliers in satellite laser ranges are discussed. A robust estimator based on an M-estimation principle is introduced. A practical calculation procedure which provides a robust criterion with high breakdown point and produces robust initial residuals for following iterative robust estimation is presented. Comparison of the results from the least-squares method with those of the robust method shows that the results of the station systematic errors from the robust estimator are more reliable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050252
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    Paper (German National Licenses)
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  • 2
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    CASA Uno GPS orbit and baseline experiments (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: CASA Uno data from sites distributed in longitude from Australia to Europe have been used to determine orbits of the GPS satellites. The characteristics of the orbits determined from double difference phase have been evaluated through comparisons of two-week solutions with one-week solutions and by comparisons of predicted and estimated orbits. Evidence of unmodeled effects is demonstrated, particularly associated with the orbit planes that experience solar eclipse. The orbit accuracy has been assessed through the repeatability of unconstrained estimated baseline vectors ranging from 245 km to 5400 km. Both the baseline repeatability and the comparison with independent space geodetic methods give results at the level of 1-2 parts in 100,000,000. In addition, the Mojave/Owens Valley (245 km) and Kokee Park/Ft. Davis (5409 km) estimates agree with VLBI and SLR to better than 1 part in 100,000,000.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 643-646
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    UT/CSR analysis of earth rotation from Lageos SLR data (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The 1983-1984 data collected by NASA and stations participating in the Crustal Dynamics Project from satellite laser ranging (SLR) systems are used to generate solutions for the earth polar motion. Solutions obtained using the MERIT Lageos standard data set are compared to operational results based on quick-look data and generated in near real-time, and the capability of Lageos SLR for the determination of earth orientation parameters (EOP) with high temporal resolution is investigated. Finally, the sensitivity of the MERIT campaign results to the number of tracking stations and to changes in the MERIT standard model is evaluated. It is concluded that the departures from the IAU/IUGG MERIT standards do not significantly change the solution and that solutions accurate at the 2 milliarcsec level can be maintained with a network of fewer than 10 appropriately selected stations.
    Keywords: GEOPHYSICS
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  • 4
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    The Seasat altimeter wet tropospheric range correction (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is found that the difference between the wet tropospheric corrections obtained with the Seasat Multichannel Microwave Radiometer (SMMR) algorithm and corrections based on near-coincident radiosonde meteorological measurements has a standard deviation of 2.79 cm, which is consistent with the independent value for water vapor determination accuracy reported by the SMMR Evaluation Team. Because the difference between the radiosonde corrections and those obtained by means of interpolated surface meteorological data has a standard deviation of 5.73 cm, the SMMR wet tropospheric correction is recommended for investigations sensitive to the wet tropospheric height correction accuracy.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 87; Apr. 30
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  • 5
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    Gravity field determination and error assessment techniques (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Linear estimation theory, along with a new technique to compute relative data weights, was applied to the determination of the Earth's geopotential field and other geophysical model parameters using a combination of satellite ground-based tracking data, satellite altimetry data, and the surface gravimetry data. The relative data weights for the inhomogeneous data sets are estimated simultaneously with the gravity field and other geophysical and orbit parameters in a least squares approach to produce the University of Texas gravity field models. New techniques to perform calibration of the formal covariance matrix for the geopotential solution were developed to obtain a reliable gravity field error estimate. Different techniques, which include orbit residual analysis, surface gravity anomaly residual analysis, subset gravity solution comparisons and consider covariance analysis, were applied to investigate the reliability of the calibration.
    Keywords: GEOPHYSICS
    Type: Ohio State Univ., Progress in the Determination of the Earth's Gravity Field; p 15-18
    Format: application/pdf
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  • 6
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    Observed temporal variations in the Earth's gravity field from 16-year Starlette orbit analysis (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Satellite laser ranging data to Starlette, collected during the period from 1975 to 1990, are analyzed to determine yearly values of the second degree annual (Sa) and semiannual (Ssa) tides, simultaneously with average values of other low degree and order tide parameters. The yearly fluctuations in the values for Sa and Ssa are associated with changes in the Earth's second degree zonal harmonic caused by meteorological excitation. The Starlette-determined mean values for the amplitude of the annual and semiannual variations in J2 are 32.3 x 10 exp -11 and 19.5 x 10 exp -11, respectively; while the rms about the mean values are 4.1 x 10 exp -11 and 6.3 x 10 exp -11, respectively. The annual delta-J2 is in good agreement with the value obtained from the combined effects of air mass redistribution without the oceanic inverted-barometer effects (non-IB) and hydrological change. Approximately 90 percent of the observed annual variation from Starlette is attributed to the meteorological mass redistribution occurring on the Earth's surface.
    Keywords: GEOPHYSICS
    Type: In: From Mars to Greenland: Charting gravity with space and airborne instruments - Fields, tides, methods, results (A93-55951 24-46); p. 83-91.
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  • 7
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    Secular variation of earth's gravitational harmonic J2 coefficient from Lageos and nontidal acceleration of earth rotation (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Analysis of 5.5 years of Lageos satellite range data reveal significant residual nodal signatures: an acceleration and annual and semiannual periods. These signatures primarily reflect variations in the zonal gravitational harmonic J2 coefficient and hence the polar moment of inertia. The implied decrease of J2 = -3 x 10 to the -11th/yr is consistent with both historical observations of the nontidal acceleration of the earth's rotation and models of viscous rebound of the solid earth from the decrease in load due to the last deglaciation.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 303; June 30
    Format: text
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  • 8
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    Comparison of earth rotation as inferred from radio interferometric, laser ranging and astrometric observations (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results of measurements of the earth's rotation vector for a 400-day period from late September 1980 to December 1981, for which date from VLBI, satellite laser ranging (SLR), and lunar laser ranging (LLR) were available, are compared. The acquisition of the data and their evaluation are described. VLBI, SLR, and classical astrometric determinations of the X-parameter required to describe the location of the rotation pole on the earth's surface are shown, and VLBI, LLR, and classical astrometric determinations of the angle of rotation about this pole (UT1) are presented. The results indicate that VLBI and SLR, at their present stages of development, yield standard errors under 20 cm in the determinations of X, about twofold smaller than obtained from classical measurements, and that VLBI and LLR yield determination of UT1 with standard errors less than 40 cm, somewhat smaller than that of the corresponding determinations from classical observations. Methods for improving these types of intercomparisons are suggested.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 302; April 7
    Format: text
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  • 9
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    Evaluation of the Seasat altimeter time tag bias (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Two methods were used in analyses of Seasat altimeter data, aimed at the corroboration of an inherent altimeter microprocessor delay compensation value of -79.4 msec, which benefited from a global data distribution in the oceanic areas: (1) the crossover method, using altimeter data differenced at points where the Seasat ground track intersected with itself, and (2) the direct use of the altimeter data. Because the former method is independent of errors in the geoid model, it is considered the more reliable. For all crossover method results, the adopted value of -79.4 msec is within the bounds of the standard deviation associated with the estimates, of which -78.1 + or - 2.0 msec is considered the best representative.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Journal of Geophysical Research; 87; Apr. 30
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  • 10
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    An improved model for the Earth's gravity field (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An improved model for the Earth's gravity field, TEG-1, was determined using data sets from fourteen satellites, spanning the inclination ranges from 15 to 115 deg, and global surface gravity anomaly data. The satellite measurements include laser ranging data, Doppler range-rate data, and satellite-to-ocean radar altimeter data measurements, which include the direct height measurement and the differenced measurements at ground track crossings (crossover measurements). Also determined was another gravity field model, TEG-1S, which included all the data sets in TEG-1 with the exception of direct altimeter data. The effort has included an intense scrutiny of the gravity field solution methodology. The estimated parameters included geopotential coefficients complete to degree and order 50 with selected higher order coefficients, ocean and solid Earth tide parameters, Doppler tracking station coordinates and the quasi-stationary sea surface topography. Extensive error analysis and calibration of the formal covariance matrix indicate that the gravity field model is a significant improvement over previous models and can be used for general applications in geodesy.
    Keywords: GEOPHYSICS
    Type: Ohio State Univ., Progress in the Determination of the Earth's Gravity Field; p 8-11
    Format: application/pdf
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