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Assessment of the new national geoid height model, GEOID03 / D.R. Roman in Surveying and land information science, vol 64 n° 3 (01/09/2004)

Public [article]  inSurveying and land information science > vol 64 n° 3 (01/09/2004) . - pp 153 - 162 Titre : Assessment of the new national geoid height model, GEOID03 Type de document : Article/Communication Auteurs : D.R. Roman, Auteur ; Y.M. Wang, Auteur ; J. Hamilton, Auteur Année de publication : 2004 Article en page(s) : pp 153 - 162 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] conversion altimétrique [Termes IGN] Etats-Unis [Termes IGN] géoïde altimétrique [Termes IGN] géoïde gravimétrique [Termes IGN] géoïde local [Termes IGN] point d'appui [Termes IGN] point de vérification Résumé : (Auteur) The GEOID03 model was developed in the same manner as GEOID99 using an underlying gravimetric geoid, USGG2003, and updated GPS ellipsoidal heights on leveled benchmarks (GPSBMs). USGG2003 is similar to G99SSS, however, it includes an updated model for gravity anomalies in the deep ocean areas, GSF00.1. The convention surface for GEOID03 was developed from 14,185 GPSBMs at a 5 arc-minute grid interval, which provided a substantial increase in the spatial coverage and reduced errors due to the interpolation. The fit to these same points afterwards was 4.8 (2s), which was comprised of both correlated (attribuate to GEOID03) and uncorrelated (GPS observation error) signals. The uncorrelated signal was 4.2 cm (2s) and correlated signal was 2.0 cm (2s), with a 3.5km correlation wavelength. GEOID03 thus had a very good fit with the GPSBMs, and can be relied upon to convert between the NAD 83 and Navd88 datums to the centimeter level. Numéro de notice : A2004-601 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27117 [article]

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Estimation of sea dynamic topography, ocean tides, and secular changes from Topex altimeter data / Y.M. Wang (1994)

Public Titre : Estimation of sea dynamic topography, ocean tides, and secular changes from Topex altimeter data Type de document : Monographie Auteurs : Y.M. Wang, Auteur ; R.H. Rapp, Auteur Editeur : Colombus (Ohio) : Ohio State University Année de publication : 1994 Collection : Department of Geodetic Science and Surveying Reports num. 430 Importance : 86 p. Format : 21 x 27 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données altimétriques [Termes IGN] fonction harmonique [Termes IGN] harmonique sphérique [Termes IGN] hauteurs de mer [Termes IGN] marée océanique [Termes IGN] perturbation séculaire [Termes IGN] TOPEX [Termes IGN] valeur efficace Résumé : (Auteur) Sea surface dynamic topography (SSDT) has been determined from the separation of the Topex sea surface height and the geoid undulations implied by the JGM-2/OSU91A merged potential coefficient model. The SSDT was initially analyzed to determine annual and semiannual variations in the ocean surface, corrections to the M2, S2, K1, 01 constituents of the Cartwright/Ray tide model, and bias and bias rate terms. All correction terms were represented by spherical series to degree 8 (for most testing purposes) and to degree 15 for final runs. The most complete analysis was done with Topex cycles 4 to 58. From this solution we found that the root mean square annual signal was ±4.5 cm in the Northern Hemisphere and ±3.5 cm in the Southern Hemisphere with an overall amplitude of ±4.0 cm. Large 'annual signals were associated with features such as the Kurishio Current (±10 cm), Gulf Stream (±7 cm) and the Falkland Current (±6 cm). The tide correction terms were ±2.9 CM (MA ±1.5 CM (S2), +0.8 CM (01), ±1.4 cm. (K1). The improvement in the tide model was proven through comparisons at the 104/95 tide gauge data set provided by C. Le Provost. The bias rate value was determined at each normal point and then averaged to determine a mean rate of 4.8 mm/yr. - After removing an altimeter drift rate of 2.0 mm/yr the net rate is 2.8 mm/yr., This rate could be a combination of sea level change and effects associated with the various correction terms applied to the data. The second main theme of the report relates to the representation of SSDT in spherical harmonics (SH) and orthonormal (ON) functions. Procedures were implemented to estimate either SH or ON coefficients. It was found that the estimation of SH coefficients was more stable than the ON estimation. For those applications on which spectral information of SSDT is needed a SH model can be transformed into an ON model. It was found that the lower degree SH coefficients are quite sensitive to the -bias correction applied to the sea surface height data. This sensitivity does not occur in ON coefficient estimation. For the analysis with data from cycles 4 to 58 a bias term of 55 cm. was applied to the data. This value leads to a zero value for the degree zero term in the ON expansion. An SH expansion to degree 24 was computed using a priori degree variance computed from 10 selected cycles of Topex data. The SH expansion was transformed to an ON expansion and both coefficient sets are given in the report. The degree 2,0 coefficient in the SH representation was -37.8 cm quite comparable with other altimeter based solutions. The analysis of the ON coefficient indicated an rms value of SSDT equal to ±61 cm. The ON- power spectrum, in conjunction with the geoid undulation accuracy of the JGM-2 model in the ocean areas, indicated the two values are approximately equal near degree 13. This suggests that SSDT estimates above degree 13 may be unreliable. This statement was consistent with the inconsistency of geostrophic flow patterns implied, by the SSDT expansions at the higher degrees. Even at the lower (e.g. 13) degree the flow patterns showed only moderate agreement with known circulation patterns. Numéro de notice : 12110 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54539

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Geoid gradients for Geosat and Topex-Poseidon repeat ground tracks / Y.M. Wang (1991)

Public Titre : Geoid gradients for Geosat and Topex-Poseidon repeat ground tracks Type de document : Monographie Auteurs : Y.M. Wang, Auteur ; R.H. Rapp, Auteur Editeur : Colombus (Ohio) : Ohio State University Année de publication : 1991 Collection : Department of Geodetic Science and Surveying Reports num. 408 Importance : 26 p. Format : 21 x 27 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] géoïde [Termes IGN] GEOSAT [Termes IGN] gradient [Termes IGN] TOPEX-Poseidon Numéro de notice : 12100 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54530

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The role of the topography in gravity gradiometer reductions and in the solution of the geodetic boundary value problem using analytical downward continuation / Y.M. Wang (1990)

Public Titre : The role of the topography in gravity gradiometer reductions and in the solution of the geodetic boundary value problem using analytical downward continuation Type de document : Monographie Auteurs : Y.M. Wang, Auteur Editeur : Colombus (Ohio) : Ohio State University Année de publication : 1990 Collection : Department of Geodetic Science and Surveying Reports num. 405 Importance : 49 p. Format : 21 x 27 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] problème des valeurs limites [Termes IGN] réduction de la pesanteur Résumé : (Auteur) The topography of the earth plays an important role in solving the geodetic boundary value problem. In this report the effect of topography on gravity gradient data is considered and the effect of topography on the solution of the geodetic boundary value problem by using analytical downward continuation is also investigated. The validity of solving Molodensky's problem by using the analytical downward continuation is inspected. Even though it has been shown that the analytical downward continuation solution is equivalent to Molodensky's solution which is considered theoretically perfect, a very small topographic effect exists. This effect is trivial and can be neglected in the numerical computations. It is also shown that a spherical harmonic expansion cannot exactly represent the disturbing potential outside the Brillouin sphere and nearby the earth at the same time. If the points are near by the earth (between the Brillouin sphere and the earth's surface), there is a topographic effect to the geopotential represented by a spherical harmonic expansion whose coefficients are determined by using the gravity anomalies analytically downward continued onto the ellipsoid. This effect is the same as to the solving of the Molodensky's problem of the analytical downward continuation is also investigated under planar approximation. It is shown that the downward continuation is convergent almost everywhere, except at the infinite point of the circular frequency w = . This is important for geopotential modeling. Provided the downward continuation is convergent, then the geopotential can be expanded into a spherical harmonic series up to very high degree and order without any theoretical difficulty. Numéro de notice : 12092 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54522

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Determination of the gravity disturbance on the earth's topographic surface from airborne gravity gradient data / Y.M. Wang (1988)

Public Titre : Determination of the gravity disturbance on the earth's topographic surface from airborne gravity gradient data Type de document : Monographie Auteurs : Y.M. Wang, Auteur Editeur : Colombus (Ohio) : Ohio State University Année de publication : 1988 Collection : Department of Geodetic Science and Surveying Reports num. 401 Importance : 47 p. Format : 21 x 27 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] champ de pesanteur terrestre [Termes IGN] gradiomètre [Termes IGN] lissage de valeur [Termes IGN] méthode des moindres carrés Numéro de notice : 12093 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54523

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Downward continuation of the free-air gravity anomalies to the ellipsoid using the gradient solution, Poisson's integral and terrain correction-numerical comparison and the computations / Y.M. Wang (1988)

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