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Symmetric neutral-atmosphere mapping functions: a review of the state-of-the-art

Sharifi M. A., Souri A. H.

Artificial Satellites : Journal of Planetary Geodesy

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2013

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Vol. 48, No. 4

159--170

EN

The aim of this paper is to review of six recent symmetric mapping functions. The mapping function can be largely used for GPS meteorological measurements, InSAR atmospheric corrections and precise measurements of very long baseline interferometry (VLBI). These spacebased techniques use radio signal that propagate through the Earth's atmosphere. The electrically-neutral region, predominantly the troposphere, affects the speed and direction of travel of radio waves leading to existence of excess path. The mapping function models the elevation angle dependence of the delay. Within the past decade, significant improvements have been achieved in order to use of Numerical Weather Models (NWM) for geodetic positioning. Ray-tracing algorithms have been performed through refractivity shells retrieved from NWMs in order to relate zenith delays to slant delays. Therefore, there seems to be a real need for deep review of recent developments in the mapping function domain. This paper proposes a comprehensive review of the symmetric mapping functions state of the art, their spatio-temporal variations and used NWM and generic models. Niell Mapping Function (NMF), Vienna Mapping Function (VMF1), University of New Brunswick-VMF1 (UNB-VMF1) mapping functions, Global Mapping Function (GMF) and Global Pressure and Temperature (GPT2)/GMF are reviewed in this paper.

2

Evaluation of symmetric neutral-atmosphere mapping functions using ray-tracing through radiosonde observations

Souri A. H., Sharifi M. A.

Artificial Satellites : Journal of Planetary Geodesy

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2013

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Vol. 48, No. 4

171--189

EN

The aim of this paper is to compare the validity of six recent symmetric mapping functions. The mapping function models the elevation angle dependence of the tropospheric delay. Niell Mapping Function (NMF), Vienna Mapping Function (VMF1), University of New BrunswickVMF1 (UNB-VMF1) mapping functions, Global Mapping Function (GMF) and Global Pressure and Temperature (GPT2)/GMF are evaluated by using ray tracing through 25 radiosonde stations covering different climatic regions in one year. The ray-traced measurements are regarded as “ground truth”. The ray-tracing approach is performed for diverse elevation angle starting at 5o to 15o . The results for both hydrostatic and non-hydrostatic components of mapping functions support the efficiency of online-mapping functions. The latitudinal dependence of standard deviation for 5o is also demonstrated. Although all the tested mapping functions can provide satisfactory results when used for elevation angles above 15o , for high precision geodetic measurements, it is highly recommended that the online-mapping functions (UNBs and VMF1) be used. The results suggest that UNB models, like VMF have strengths and weaknesses and do not stand out as being consistently better or worse than the VMF1. The GPT2/GMF provided better accuracy than GMF and NMF. Since all of them do not require site specific data; therefore GPT2/GMF can be useful as regards its ease of use.

3

Stiffness and mass matrices of FEM applicable dynamic infinite element with united shape basis

Kazakov K.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 1

189-200

EN

This paper is devoted to the construction and evaluation of mass and stiffness matrices of elastodynamic four and five node infinite elements with united shape functions (EIEUSF), recently proposed by the author. Such elements can be treated as family elastodynamic infinite elements appropriate for multi-wave soil-structure interaction problems. The common characteristic of the proposed infinite elements is the so-called united shape function, based on finite number of wave shape functions. The idea and the construction of the united shape basis are described in brief. This element belongs to decay class infinite elements. It is shown that by appropriate mapping functions the formulation of such an element can be easily transformed to a mapped form. The results obtained using the proposed infinite elements are in a good agreement with the superposed results obtained by series of standard computational models. The continuity along the finite/infinite element (artificial boundary) line in two-dimensional substructure models is also discussed in brief. In this type of computational models such a line marks the artificial boundary between the near and the far field of the model.

4

Concept of mapped Infinite Elements incorporated into Boundary Element Method

Pańczyk M., Sikora J.

Przegląd Elektrotechniczny

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2007

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R. 83, nr 11

25-28

EN

Incorporation of Infinite Elements into Boundary Element Method (BEM) requires to introduce special mapping functions or combination of standard shape function and decay functions for infinite region. The concept of mapped infinite elements usage and their implication for calculation steps in BEM will be presented. Results will be illustrated by two-dimensional example. It is to clarify the application of infinite elements into existing BEM software.

PL

Zastosowanie elementów brzegowych nieskończonych w Metodzie Elementów Brzegowych (MEB) wymaga użycia specjalnych funkcji transformujących geometrię lub połączenia standardowych funkcji kształtu z funkcjami zaniku. Schemat wprowadzenia elementów brzegowych nieskończonych z transformacją geometrii do MEB zostanie przedstawiony i zilustrowany na prostym dwu-wymiarowym przykładzie. Celem jest prześledzenie metodyki włączenia elementów nieskończonych do istniejących programów MEB.