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Auteur M. Leismann
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Untersuchungen verschiedener Höhensysteme, dargestellt an einer Testschleife in Rheinland-Pfalz / M. Leismann (1992)
Titre : Untersuchungen verschiedener Höhensysteme, dargestellt an einer Testschleife in Rheinland-Pfalz Titre original : [Études de différents systèmes d'altitudes, représentés par une boucle de test en Rhénanie-Palatinat] Type de document : Monographie Auteurs : M. Leismann, Auteur ; R. Klees, Auteur ; H. Beckers, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 1992 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 296 Importance : 97 p. Format : 21 x 30 cm - cont. 7 planches ISBN/ISSN/EAN : 978-3-7696-8580-0 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] altitude normale
[Termes IGN] hauteur ellipsoïdale
[Termes IGN] positionnement par GPS
[Termes IGN] Rhénanie-Palatinat (Allemagne)
[Termes IGN] système de référence altimétrique
Résumé : (Auteur) This report deals with the examination of several height systems for practical and scientific purposes. It starts with a short introduction to the height problem including the formulation of a catalog of demands coming from science, administration, planning and economy. Section 2 contains some foundations about the gravity field of a level ellipsoid, the theoretical closing error that would be obtained by errorless levelling from a starting point, around a level circuit, and back to the starting point and methods for gravity reduc-tions. In section 3 the different height systems being part of our examination are defined. Besides the geo-potential numbers and the dynamic heights we especially consider the orthometric heights and their differ-ent realizations restricting ourselves to those systems which can be determined from levelling and gravity measurements only; for other orthometric heights like Niethammer, Mader and Mueller we summarize the most important facts taken from known publications. Besides, we consider several normal heights, the so called spheroidal-orthometric heights presently used in Germany and the ellipsoidal heights as the only strictly geometrically defined height system. In section 4 we describe the properties of the different height systems and compare them with the catalog of demands mentioned before. The numerical calculations presented in section 5 are based on a closed 420 km levelling line located in the southwestern part of Germany with heights between 60 m and 700 m.
The results show that none of the considered height systems meets all the requirements listed in section 1. That is why we propose the use of two systems; one for purposes placing the dynamic interpretation of heights in the foreground and the other to cover all the geometric tasks most important for piirely geodetic purposes and coming up from modern satellite techniques like NAVSTAR/GPS and inertial methods.
In our opinion, from all the examined height systems the normal heights of Molodensky are the best compro-mise for all users leading to the best compensation between all the requirements. This height system is in contrast to the presently used spheroidal-orthometric system path independent, i.e. independent of the levelling route. In relation to the geopotential numbers and the dynamic heights they have a geometric interpretation, i.e. they define the distance of a point on the earth's surface from the quasigeoid, a surface differing from the geoid by some few centimeters or decimeters; only in some high mountain regions differ-ences up to 2 meters are possible. Its main advantage is especially in comparison with orthometric heights - that it is free from any hypotheses about the variation of gravity within the earth's crust and the isostatic compensation depth so that the accuracy of normal heights depends only on the accuracy of the measured gravity values and the levelling. Compared with the orthometric heights they suffer from the fact that the quasigeoid is not an equipotential surface of the earth's gravity field making the understanding of the heights possibly difficult for some practitioners. The corrections being taken into account to transform the results of levelling into normal heights and normal height differences are comparable to those for orthome-tric heights but greater than the spheroidal-orthometric corrections. But, for most of the practitioners they are not so hard to accept as the very large dynamic corrections. A disadvantage compared with dynamic heights is the fact that surfaces of equal normal heights are not identical with equipotential surfaces of the earth's gravity field. But the differences are very small and have to be considered only in some special cases like hydrologic projects where sometimes high accuracies are required. For geodetic purposes the geometric interpretation of heights is placed in the foreground, particularly in view of the great progress in satellite geodesy especially satellite positioning techniques like NAVSTAR/GPS and inertia! methods so that three dimensional geodesy will become more and more important even for local applications. In that sense ellipsoidal heights should be used as the fundamental geometric height system and should be incorporated into existing geodetic data bases.
Numéro de notice : 28219 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=63565
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Code-barres Cote Support Localisation Section Disponibilité 28219-01 30.10 Livre Centre de documentation Géodésie Disponible 28219-02 30.10 Livre Centre de documentation Géodésie Disponible