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What does height really mean? Part 2: physics and gravity / Thomas H. Meyer in Surveying and land information science, vol 65 n° 1 (01/03/2005)

Public [article]  inSurveying and land information science > vol 65 n° 1 (01/03/2005) . - pp 5 - 15 Titre : What does height really mean? Part 2: physics and gravity Type de document : Article/Communication Auteurs : Thomas H. Meyer, Auteur ; D.R. Roman, Auteur ; David B. Zilkoski, Auteur Année de publication : 2005 Article en page(s) : pp 5 - 15 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] altitude [Termes IGN] ellipsoïde (géodésie) [Termes IGN] force de gravitation [Termes IGN] géoïde [Termes IGN] gravimétrie [Termes IGN] niveau moyen des mers [Termes IGN] nivellement par GPS [Termes IGN] potentiel de pesanteur terrestre Résumé : (Auteur) This is the second paper in a four-part series considering the fundamental question, "what does the word height really mean ?" The first paper in this series explained that a change in National Geodetic Survey's policy, coupIed with the modern realities of GPS surveving, have essentially forced practicing surveyors to come to grips with the myriad of height definitions that previously were the sole concern of geodesists. The distinctions between local and equipotential ellipsoids were considered, along with an introduction to mean sea level. This paper brings these ideas foward by explaining mean sea level and, more importantly, the geoid. The discussion is grounded in physics from which gravitational force and potential energy will be considered, leading to a simple derivation of the shape of the Earth's gravity field. This lays the foundation for a simplistic model of the geoid near Mt. Everest, which will be used to explain the undulations in the geoid across the entire Earth. The terms geoid, plumb line, potential, equipotential surface, geopotential number and mean sea level will be explained, including a discussion of why mean sea level is not everywhere the same height, why it is not a level surface. Numéro de notice : A2005-280 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27416 [article]

Voir aussi

• What does height really mean? Part 1: Introduction / Thomas H. Meyer in Surveying and land information science, vol 64 n° 4 (01/12/2004)
• What does height really mean? Part 3 height systems / Thomas H. Meyer in Surveying and land information science, vol 66 n° 2 (01/09/2006)

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Analysis of the design parameters of multi-reference station RTK GPS networks / Ahmed El-Mowafy in Surveying and land information science, vol 65 n° 1 (01/03/2005)

Public [article]  inSurveying and land information science > vol 65 n° 1 (01/03/2005) . - pp 17 - 26 Titre : Analysis of the design parameters of multi-reference station RTK GPS networks Type de document : Article/Communication Auteurs : Ahmed El-Mowafy, Auteur Année de publication : 2005 Article en page(s) : pp 17 - 26 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] Doubaï [Termes IGN] GPS en mode cinématique [Termes IGN] ligne de base [Termes IGN] positionnement cinématique en temps réel [Termes IGN] réseau géodésique local [Termes IGN] station de référence [Termes IGN] station GPS [Termes IGN] station virtuelle [Termes IGN] tachéomètre électronique [Termes IGN] temps réel Résumé : (Auteur) In this study, the main design parameters of multi-reference station RTK-GPS networks have been analyzed, and their impact on the achieved positioning performance and phase ambiguity resolution is discussed. The main parameters considered are: the distance separating reference stations, network configuration, communication between the computing center and the user, and network algorithm. A number of tests have been conducted in a case study utilizing the Dubai Virtual Reference Network System (DVRS) in the United Arab Emirates. First, the real-time performance of the existing network was assessed. Next, the performance of the network was evaluated in a post-mission processing after making changes to its design, addressing the above parameters, by adding data from three auxiliary reference stations. Different network configurations were examined, consisting of variable combinations of the DVRS and the auxiliary stations. In addition, positioning results of two network algorithms (FKP/VRS and the Multiref methods) were compared. Finally, recommendations concerning the selection of baseline lengths, network architecture and station redundancy have been given. Numéro de notice : A2005-281 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27417 [article]

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Delaunay triangulation structured kriging for surface interpolation / Yaron Felus in Surveying and land information science, vol 65 n° 1 (01/03/2005)

Public [article]  inSurveying and land information science > vol 65 n° 1 (01/03/2005) . - pp 27 - 36 Titre : Delaunay triangulation structured kriging for surface interpolation Type de document : Article/Communication Auteurs : Yaron Felus, Auteur ; A. Saaled, Auteur ; Burkhard Schaffrin, Auteur Année de publication : 2005 Article en page(s) : pp 27 - 36 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] Antarctique [Termes IGN] champ géomagnétique [Termes IGN] erreur moyenne quadratique [Termes IGN] interpolation linéaire [Termes IGN] krigeage [Termes IGN] système d'information géographique [Termes IGN] Triangulated Irregular Network [Termes IGN] triangulation de Delaunay Résumé : (Auteur) Surface interpolation is an essential tool in surveying and geographical information systems projects. For example, given a list of observations (e.g. elevations, gravity or magnetic field values, and underground-water levels), a prediction of a value at an unobserved location is made. Surveyors and engineers commonly use Triangulated Irregular Network (TIN) based linear interpolation for surface interpolation. TIN interpolation is computationally very efficient, utilizing a Delaunay triangulation algorithm and simple mathematical function. However, the TIN method uses only three local data points. Therefore, it is often less accurate and will yield a higher Mean Square Prediction Error (MSPE). Kriging is a relatively new, accurate interpolation method which yields a smaller Mean Square Prediction Error (MSPE). Nevertheless, kriging is computationally inefficient and requires the inversion of an nxn matrix where n is the number of data points. A unique approach is presented here that combines these two techniques such that the Delaunay triangulation data-structure is used to determine the interpolation neighborhood of a kriging prediction process. The new TIN-based kriging algorithm is used to interpolate aeromagnetic data for a geographical information system developed in West Antarctica. A comparison is made between global kriging, TIN linear interpolation, and the TIN-structured kriging. Numéro de notice : A2005-284 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27420 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
121-05011	RAB	Revue	Centre de documentation	En réserve L003	Disponible