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The use of gravity data to determine orthometric heights at the Hong Kong territories / Albertini Nsiah Ababio in Journal of applied geodesy, vol 16 n° 4 (October 2022)  

Public [article]  inJournal of applied geodesy > vol 16 n° 4 (October 2022) . - pp 401 - 416 Titre : The use of gravity data to determine orthometric heights at the Hong Kong territories Type de document : Article/Communication Auteurs : Albertini Nsiah Ababio, Auteur ; Robert Tenzer, Auteur Année de publication : 2022 Article en page(s) : pp 401 - 416 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] altitude orthométrique [Termes IGN] correction orthométrique [Termes IGN] Hong-Kong [Termes IGN] interpolation [Termes IGN] levé gravimétrique [Termes IGN] montagne [Termes IGN] système de référence local [Vedettes matières IGN] Altimétrie Résumé : (auteur) The Hong Kong Principal Datum (HKPD) is the currently adopted official geodetic vertical datum at the Hong Kong territories. The HKPD is practically realized by heights of levelling benchmarks. The HKPD heights are, however, neither normal nor orthometric. The reason is that heights of levelling benchmarks were determined from precise levelling measurements, but without involving gravity observations along levelling lines. To reduce systematic errors due to disregarding the gravity information along levelling lines, we used terrestrial and marine gravity data to interpolate gravity values at levelling benchmarks in order to compute and apply the orthometric correction to measured levelling height differences. Our results demonstrate the importance of incorporating the gravity information even for a relatively small region but characterized by a rough topography with heights of levelling benchmarks exceeding several hundreds of meters. According to our estimates, the orthometric correction reaches (and even slightly exceeds) ±2 cm, with maxima along levelling lines crossing mountain chains. Numéro de notice : A2022-742 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2022-0012 Date de publication en ligne : 04/08/2022 En ligne : https://doi.org/10.1515/jag-2022-0012 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101724 [article]

Contribution of mass density heterogeneities to the quasigeoid-to-geoid separation / Robert Tenzer in Journal of geodesy, vol 90 n° 1 (January 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 1 (January 2016) . - pp 65-80 Titre : Contribution of mass density heterogeneities to the quasigeoid-to-geoid separation Type de document : Article/Communication Auteurs : Robert Tenzer, Auteur ; Christian Hirt, Auteur ; Pavel Novák, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 65-80 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] harmonique sphérique [Termes IGN] masse de la Terre [Termes IGN] modèle de densité [Termes IGN] quasi-géoïde [Termes IGN] topographie Résumé : (auteur) The geoid-to-quasigeoid separation is often computed only approximately as a function of the simple planar Bouguer gravity anomaly and the height of the computation point while disregarding the contributions of terrain geometry and anomalous topographic density as well as the sub-geoid masses. In this study we demonstrate that these contributions are significant and, therefore, should be taken into consideration when investigating the relation between the normal and orthometric heights particularly in the mountainous, polar and geologically complex regions. These contributions are evaluated by applying the spectral expressions for gravimetric forward modelling and using the EIGEN-6C4 gravity model, the Earth2014 datasets of terrain, ice thickness and inland bathymetry and the CRUST1.0 sediment and (consolidated) crustal density data. Since the global crustal density models currently available (e.g. CRUST1.0) have a limited accuracy and resolution, the comparison of individual density contributions is—for consistency—realized with a limited spectral resolution up to a spherical harmonic degree 360 (or 180). The results reveal that the topographic contribution globally varies between −0.33 and 0.57 m, with maxima in Himalaya and Tibet. The contribution of ice considerably modifies the geoid-to-quasigeoid separation over large parts of Antarctica and Greenland, where it reaches ∼0.2 m. The contributions of sediments and bedrock are less pronounced, with the values typically varying only within a few centimetres. These results, however, have still possibly large uncertainties due to the lack of information on the actual sediment and bedrock density. The contribution of lakes is mostly negligible; its maxima over the Laurentian Great Lakes and the Baikal Lake reach only several millimetres. The contribution of the sub-geoid masses is significant. It is everywhere negative and reaches extreme values of −4.43 m. According to our estimates, the geoid-to-quasigeoid separation globally varies within −4.19 and 0.26 m while the corresponding values computed according to a classical definition are only negative and reach extreme values of −3.5 m. A comparison of these results reveals that inaccuracies caused by disregarding the terrain geometry and mass density heterogeneities distributed within the topography and below the geoid surface can reach ±2 m or more in the mountainous regions. Numéro de notice : A2016-019 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0858-5 Date de publication en ligne : 01/10/2015 En ligne : https://doi.org/10.1007/s00190-015-0858-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79466 [article]

Empirical model of the gravitational field generated by the oceanic lithosphere / Robert Tenzer in Advances in space research, vol 55 n° 1 ([01/01/2015])  

Public [article]  inAdvances in space research > vol 55 n° 1 [01/01/2015] . - pp 72 - 82 Titre : Empirical model of the gravitational field generated by the oceanic lithosphere Type de document : Article/Communication Auteurs : Robert Tenzer, Auteur ; W. Chen, Auteur ; Zhourun Ye, Auteur Année de publication : 2015 Article en page(s) : pp 72 - 82 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de gravitation [Termes IGN] champ de pesanteur terrestre [Termes IGN] harmonique sphérique [Termes IGN] isostasie [Termes IGN] lithosphère [Termes IGN] modèle empirique [Termes IGN] océan Résumé : (auteur) We present an empirical model of the gravitational field generated by the oceanic lithosphere computed over the world’s oceans with a spectral resolution complete to a spherical harmonic degree of 180. This gravity model is compiled based on applying methods for a spherical harmonic analysis and synthesis of the global gravity and crustal structure models. The in situ seawater densities and the density samples from ocean-floor drilling sites are utilized in the gravimetric forward modeling of bathymetry and marine sediments. The gravitational signal attributed to the oceanic lithosphere density structure is described empirically in terms of the ocean-floor age and depth. The former is explained by the increasing density with age due to conductive cooling of the oceanic lithosphere. The latter describes the gravitational signature of thermal lithospheric contraction, which is isostatically compensated by ocean deepening. The long-wavelength gravity spectrum reflects mainly the compositional and thermal structures within the sub-lithospheric mantle. We demonstrate that this empirical gravity model reproduces realistically most of the long-to-medium wavelength features of the actual gravity field, except for some systematic discrepancies, especially along continental slopes and large sedimentary accumulations, which cannot be described accurately by applied empirical models. Numéro de notice : A2015-296 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2014.09.023 En ligne : https://doi.org/10.1016/j.asr.2014.09.023 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76456 [article]

New Zealand 20th century sea level rise : Resolving the vertical land motion using space geodetic and geological data / Abdelali Fadil in Journal of geophysical research : Oceans, vol 118 n° 11 (November 2013)  

Public [article]  inJournal of geophysical research : Oceans > vol 118 n° 11 (November 2013) . - pp 6076 - 6091 Titre : New Zealand 20th century sea level rise : Resolving the vertical land motion using space geodetic and geological data Type de document : Article/Communication Auteurs : Abdelali Fadil, Auteur ; Paul Denys, Auteur ; Robert Tenzer, Auteur ; Hugh R. Grenfell, Auteur ; Pascal Willis , Auteur Année de publication : 2013 Article en page(s) : pp 6076 - 6091 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] données géologiques [Termes IGN] données marégraphiques [Termes IGN] marais salé [Termes IGN] montée du niveau de la mer [Termes IGN] Nouvelle-Zélande Résumé : (Auteur) Investigations in long‐term instrumental tidal records reveal that 20th century sea level along the coast of New Zealand is rising at 1.46 ± 0.10 mm/yr in agreement with the regional rates from southern Australia and Tasmania. We extend the advanced altimeter‐gauge approach of combining satellite altimetry and tide gauge data with constraint equations from long‐term adjacent tide gauge records to assess its performance in open seas and to explore the impact of vertical land motion on the observed relative sea level. This approach has again proven to be a robust method with an accuracy of 0.4 mm/yr. While no clear sea level rise pattern can be inferred once the tide gauge apparent sea level trends are corrected for vertical land motions from GPS, the advanced altimeter‐gauge and geological vertical rates are completely consistent and reveal three temporal phases of sea level rise marked by an increase from 1.46 ± 0.10 mm/yr to 1.72 ± 0.10 mm/yr during the period (1900–1936), followed by a decrease to 1.48 ± 0.10 mm/yr during the period (1936–1956), and a substantial increase to 2.60 ± 0.10 mm/yr during the period (1956–1975). In contrast, the 20th century microfossil proxy records of absolute sea level rise display twice the tide gauge sea level rise rate of 3.17 ± 0.30 mm/yr and 3.28 ± 0.45 mm/yr, respectively, once salt‐marsh records are corrected using GPS and geological vertical rates. Differential autocompaction and transfer functions are possible factors, which need further investigation. Numéro de notice : A2013-839 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1002/2013JC008867 Date de publication en ligne : 22/10/2013 En ligne : https://doi.org/10.1002/2013JC008867 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91302 [article]

A data-driven approach to local gravity field modelling using spherical radial basis functions / R. Klees in Journal of geodesy, vol 82 n° 8 (August 2008)  

Public [article]  inJournal of geodesy > vol 82 n° 8 (August 2008) . - pp 457 - 471 Titre : A data-driven approach to local gravity field modelling using spherical radial basis functions Type de document : Article/Communication Auteurs : R. Klees, Auteur ; Robert Tenzer, Auteur ; I. Prutkin, Auteur ; Tobias Wittwer, Auteur Année de publication : 2008 Article en page(s) : pp 457 - 471 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] champ de pesanteur local [Termes IGN] fonction de base radiale [Termes IGN] hauteur ellipsoïdale [Termes IGN] nivellement par GPS [Termes IGN] Pays-Bas [Termes IGN] problème des valeurs limites Résumé : (Auteur) We propose a methodology for local gravity field modelling from gravity data using spherical radial basis functions. The methodology comprises two steps: in step 1, gravity data (gravity anomalies and/or gravity disturbances) are used to estimate the disturbing potential using least-squares techniques. The latter is represented as a linear combination of spherical radial basis functions (SRBFs). A data-adaptive strategy is used to select the optimal number, location, and depths of the SRBFs using generalized cross validation. Variance component estimation is used to determine the optimal regularization parameter and to properly weight the different data sets. In the second step, the gravimetric height anomalies are combined with observed differences between global positioning system (GPS) ellipsoidal heights and normal heights. The data combination is written as the solution of a Cauchy boundary-value problem for the Laplace equation. This allows removal of the non-uniqueness of the problem of local gravity field modelling from terrestrial gravity data. At the same time, existing systematic distortions in the gravimetric and geometric height anomalies are also absorbed into the combination. The approach is used to compute a height reference surface for the Netherlands. The solution is compared with NLGEO2004, the official Dutch height reference surface, which has been computed using the same data but a Stokes-based approach with kernel modification and a geometric six-parameter “corrector surface” to fit the gravimetric solution to the GPS-levelling points. A direct comparison of both height reference surfaces shows an RMS difference of 0.6 cm; the maximum difference is 2.1 cm. A test at independent GPS-levelling control points, confirms that our solution is in no way inferior to NLGEO2004. Copyright Springer Numéro de notice : A2008-319 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0196-3 En ligne : https://doi.org/10.1007/s00190-007-0196-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29312 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-08071	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-08072	RAB	Revue	Centre de documentation	En réserve L003	Disponible