GPS Alignment Surveys and Meridian Convergence

Soler, Tomás; Fury, Rudolf J.

doi:10.1061/(asce)0733-9453(2000)126:3(69)

Cited by 9 publications

(3 citation statements)

References 9 publications

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“…At all longitudes except for the longitude of the grid center, the field data are now oriented at an angle to the grid north (or Cartesian x-axis): in the Northern Hemisphere, they point inward, whereas in the Southern Hemisphere, they point outward relative to the Cartesian grid north. This phenomenon is best known as meridian convergence and is well recognized and corrected for in geodesy and cartography (Reilly and Bibby, 1975;Soler and Fury, 2000). For continental-scale magnetotelluric applications, meridian convergence is yet another effect contributing to the inaccuracy of the Cartesian approximation and needs to be accounted for and corrected within the framework of this comparison.…”

Section: Meridian Convergencementioning

confidence: 99%

Three-dimensional magnetotelluric modeling in the spherical and Cartesian coordinate systems: A comparative study

Han¹,

Hu²

2023

Earth and Planetary Physics

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A newly developed regional spherical magnetotelluric program was used to evaluate simulation differences qualitatively and quantitatively with respect to the use of traditional Cartesian coordinates.q Model conversion from spherical to Cartesian coordinate and meridian convergence in impedance was introduced to guarantee the rationality of comparison.qThe calculation results of real three-dimensional electrical conductivity models prove that the Earth's curvature cannot be neglected in large-scale magnetotelluric exploration.

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Section: Meridian Convergencementioning

confidence: 99%

Three-dimensional magnetotelluric modeling in the spherical and Cartesian coordinate systems: A comparative study

Han¹,

Hu²

2023

Earth and Planetary Physics

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“…(2) [6,7]. The commonest conversion adopted for determining convergence is the Gauss-Bomford convention.…”

Section: Theoretical Relationship Between Azimuthsmentioning

confidence: 99%

Grid, Geodetic and Astronomical Azimuth Conversions in Ghana

Ayer¹,

Asante²,

Ziggah³

et al. 2022

WJGG

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Astronomic azimuths had been used for orienting old surveys in Ghana. With technological advancement and the development of simpler but accurate equipment and techniques for measurement, this has been replaced by the use of the Global Navigational Satellite System (GNSS) techniques such as the Global Positioning System(GPS). However, the use of these for azimuth determinations results in a different type of azimuth as opposed to astronomic azimuths previously used. For retracing some of those old surveys based on Astronomical coordinates, the relationship and convertibility between the different azimuths is imperative. In this exploration, the relationship and precision of both techniques were tested on various baselines located in different parts of the country. This involved the computation of Astronomic, Geodetic and Grid Azimuths between pairs of points to form several baselines. These baselines span from the Southern to the Middle belt portions of the Country where triangulations have been done, as some of these triangulation stations were Laplace stations that have both astronomic and geodetic coordinates determined for them. The results were investigated in terms of effect of using the convergence and t-T correction to convert between the set of azimuths. The results show that Geodetic Azimuths could be converted to grid coordinates and vice versa to accuracies of mean 0° 0ʹ 0.56ʺ and standard deviation ± 5.6 seconds. However, for Astronomic to Grid Azimuths, without correcting for Deflection of vertical, the conversion is accurate only to mean differences of 0° 1ʹ 25.3ʺ with standard deviation ± 0° 8ʹ 21.5ʺ. The results show the necessity of the Laplace correction for vertical deflection in astronomic azimuths in addition to the convergence and t-T correction and recommends the provision of country-wide deflection corrections.

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“…The meridians convergence in refl ection is an angle between the tangents towards the meridian image at a given spot, and the straight line going through that point perpendicularly towards the x axis ( Fig. 1) (Soler and Fury 2000).…”

Section: A Topographic Azimuth In 2000 Distributionmentioning

confidence: 99%

Design, measurement and analysis of gyro-azimuths influence on the results of aligning the underground control network

Szafarczyk¹,

Młynarczyk

Markiewicz

et al. 2017

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The article discusses the impact of additionally measured gyroazimuths on the accuracy of the underground network. It discusses such issues as: the way of gyroazimuth measurement, corrections introduced into the measured gyroazimuth, eff ects of centering the instrument and signal and eff ects of side lengths for accuracy of gyroazimuth measurement, the legal basis for such measurement in mining excavations and design quantities and location of gyroazimuth measurement in the underground network to obtain its better accuracy. These theoretical arguments have been illustrated on the example of gyroazimuths measurement on the fi ve sides of the existing underground network mainly focused on increasing its accuracy parameters by this additional measurement. PROJEKT, POMIAR I ANALIZA WPŁYWU GIROAZYMUTÓW NA WYNIKI WYRÓWNANIA OSNOWY PODZIEMNEJ Słowa kluczowe: giroskop, pomiar azymutu, wyrównanie osnowy podziemnej Abstrakt W artykule poruszono problematykę wpływu dodatkowo pomierzonych giroazymutów na dokładność osnowy podziemnej. Omówiono w nim takie zagadnienia jak: sposób pomiaru giroazimutu, poprawki wprowadzane do pomierzonych giroazymutów, wpływ ekscentrów stanowiska instrumentu i sygnału oraz długości boku na dokładność pomiaru giroazymutu, podstawy prawne takiego pomiaru w wyrobiskach górniczych oraz sposób projektowania ilości i miejsca pomiaru giroazymutu w sieci dołowej pozwalający uzyskać podwyższenie dokładności sieci dołowej. Podstawy teoretyczne zilustrowane zostały przykładem z pomiaru giroazymutów na pięciu bokach istniejącej sieci dołowej głównie pod kątem uzyskanego podwyższenia tym dodatkowym pomiarem jej parametrów dokładnościowych.

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GPS Alignment Surveys and Meridian Convergence

Cited by 9 publications

References 9 publications

Three-dimensional magnetotelluric modeling in the spherical and Cartesian coordinate systems: A comparative study

Three-dimensional magnetotelluric modeling in the spherical and Cartesian coordinate systems: A comparative study

Grid, Geodetic and Astronomical Azimuth Conversions in Ghana

Design, measurement and analysis of gyro-azimuths influence on the results of aligning the underground control network

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