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Systematic effects in laser scanning and visualization by confidence regions / Karl Rudolf Koch in Journal of applied geodesy, vol 10 n° 4 (December 2016)
[article]
Titre : Systematic effects in laser scanning and visualization by confidence regions Type de document : Article/Communication Auteurs : Karl Rudolf Koch, Auteur ; Jan Martin Brockmann, Auteur Année de publication : 2016 Article en page(s) : pp 247 – 257 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] carte de confiance
[Termes IGN] covariance
[Termes IGN] densité de probabilité
[Termes IGN] distribution de Gauss
[Termes IGN] données lidar
[Termes IGN] données localisées 3D
[Termes IGN] ellipsoïde (géodésie)
[Termes IGN] itération
[Termes IGN] matrice de covariance
[Termes IGN] mesure géométrique
[Termes IGN] méthode de Monte-Carlo
[Termes IGN] série temporelle
[Termes IGN] visualisationRésumé : (auteur) A new method for dealing with systematic effects in laser scanning and visualizing them by confidence regions is derived. The standard deviations of the systematic effects are obtained by repeatedly measuring three-dimensional coordinates by the laser scanner. In addition, autocovariance and cross-covariance functions are computed by the repeated measurements and give the correlations of the systematic effects. The normal distribution for the measurements and the multivariate uniform distribution for the systematic effects are applied to generate random variates for the measurements and random variates for the measurements plus systematic effects. Monte Carlo estimates of the expectations and the covariance matrix of the measurements with systematic effects are computed. The densities for the confidence ellipsoid for the measurements and the confidence region for the measurements with systematic effects are obtained by relative frequencies. They only depend on the size of the rectangular volume elements for which the densities are determined. The problem of sorting the densities is solved by sorting distances together with the densities. This allows a visualization of the confidence ellipsoid for the measurements and the confidence region for the measurements with systematic effects. Numéro de notice : A2016-975 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1515/jag-2016-0012 En ligne : https://doi.org/10.1515/jag-2016-0012 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83682
in Journal of applied geodesy > vol 10 n° 4 (December 2016) . - pp 247 – 257[article]A conventional value for the geoid reference potential W0 / L. Sánchez in Journal of geodesy, vol 90 n° 9 (September 2016)
[article]
Titre : A conventional value for the geoid reference potential W0 Type de document : Article/Communication Auteurs : L. Sánchez, Auteur ; Robert Cunderlik, Auteur ; N. Dayoub, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 815 - 835 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] données GOCE
[Termes IGN] données GRACE
[Termes IGN] force de gravitation
[Termes IGN] géoïde terrestre
[Termes IGN] potentiel de pesanteur terrestre
[Termes IGN] surface de la mer
[Termes IGN] télémétrie laser sur satelliteRésumé : (auteur) W0 is defined as the potential value of a particular level surface of the Earth’s gravity field called the geoid. Since the most accepted definition of the geoid is understood to be the equipotential surface that coincides with the worldwide mean ocean surface, a usual approximation of W0 is the averaged potential value WS at the mean sea surface. In this way, the value of W0 depends not only on the Earth’s gravity field modelling, but also on the conventions defining the mean sea surface. W0 computations performed since 2005 demonstrate that current published estimations differ by up to −2.6 m2 s−2 (corresponding to a level difference of about 27 cm), which could be caused by the differences in the treatment of the input data. The main objective of this study is to perform a new W0 estimation relying on the newest gravity field and sea surface models and applying standardised data and procedures. This also includes a detailed description of the processing procedure to ensure the reproducibility of the results. The following aspects are analysed in this paper: (1) sensitivity of the W0 estimation to the Earth’s gravity field model (especially omission and commission errors and time-dependent Earth’s gravity field changes); (2) sensitivity of the W0 estimation to the mean sea surface model (e.g., geographical coverage, time-dependent sea surface variations, accuracy of the mean sea surface heights); (3) dependence of the W0 empirical estimation on the tide system; and (4) weighted computation of the W0 value based on the input data quality. Main conclusions indicate that the satellite-only component (n=200) of a static (quasi-stationary) global gravity model is sufficient for the computation of W0. This model should, however, be based on a combination of, at least, satellite laser ranging (SLR), GRACE and GOCE data. The mean sea surface modelling should be based on mean sea surface heights referring to a certain epoch and derived from a standardised multi-mission cross-calibration of several satellite altimeters. We suggest that the uncertainties caused by geographically correlated errors, including shallow waters in coastal areas and sea water ice content at polar regions should be considered in the computation of W0 by means of a weighed adjustment using the inverse of the input data variances as a weighting factor. This weighting factor should also include the improvement provided by SLR, GRACE and GOCE to the gravity field modelling. As a reference parameter, W0 should be time-independent (i.e., quasi-stationary) and it should remain fixed for a long-term period (e.g., 20 years). However, it should have a clear relationship with the mean sea surface level (as this is the convention for the realisation of the geoid). According to this, a suitable recommendation is to adopt a potential value obtained for a certain epoch as the reference value W0 and to monitor the changes of the mean potential value at the sea surface WS. When large differences appear between W0 and WS (e.g., >±2 m2 s−2), the adopted W0 may be replaced by an updated (best estimate) value. In this paper, the potential value obtained for the epoch 2010.0 (62,636,853.4 m2 s−2) is recommended as the present best estimate for the W0 value. It differs −2.6 m2 s−2 from the so-called IERS W0 value (62,636,856.0 m2 s−2), which corresponds to the best estimate available in 1998. Numéro de notice : A2016-655 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0913-x En ligne : http://dx.doi.org/10.1007/s00190-016-0913-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81857
in Journal of geodesy > vol 90 n° 9 (September 2016) . - pp 815 - 835[article]Recovery of cadastral boundaries with GNSS equipment / A. Cina in Survey review, vol 48 n° 350 (September 2016)
[article]
Titre : Recovery of cadastral boundaries with GNSS equipment Type de document : Article/Communication Auteurs : A. Cina, Auteur ; A. M. Manzino, Auteur ; G. Manzino, Auteur Année de publication : 2016 Article en page(s) : pp 338 - 346 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cadastre étranger
[Termes IGN] appariement de données localisées
[Termes IGN] cadastre ancien
[Termes IGN] cadastre numérique
[Termes IGN] ellipsoïde de Bessel
[Termes IGN] Italie
[Termes IGN] limite cadastrale
[Termes IGN] numérisation du cadastre
[Termes IGN] positionnement par GNSS
[Termes IGN] projection
[Termes IGN] système de référence localRésumé : (auteur) The purpose of this work is to propose a new redefinition of cadastral boundaries using GNSS equipment and cadastral maps. These maps are the ‘original’ maps of the Italian Land Cadastre, the first cartographic support built directly from measures carried out by technicians during implantation of the Italian land cadastre. They are called ‘originali di impianto’ – ‘originals of implantation’ or ‘implant maps’. As such, these maps are valuable and are kept with great care. Recently, the Italian cadastre has carried out an accurate digitisation of these maps in a raster format at a high resolution. In this work, the authors propose the use of these digital maps for the recovery of cadastral boundary. The original cadastral map, one of the primary sources relied upon in defining legal boundaries, generally uses the Bessel ellipsoid localised in Genova and the Cassini-Soldner projection; the GNSS equipment, on the other hand, uses the geocentric ellipsoid with global or continental realisations. After an RTK positioning, the receivers usually provide the cartographic coordinates in a Gauss projection. However, our study deals with the problem of using different projections and reference systems within the limits of a map. In this context, the transition between systems and projections can be made through a conformal transformation with deformations slighter than graphical errors in the map. The difficulty of finding identifiable points in both reference systems is partially solved through a new way of carrying out the redefinition of boundaries by exploiting geometric information. Numéro de notice : A2016-641 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000007 En ligne : https://doi.org/10.1179/1752270615Y.0000000007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81846
in Survey review > vol 48 n° 350 (September 2016) . - pp 338 - 346[article]The SMITSWAM method of datum transformations consisting of Standard Molodensky in two stages with applied misclosures / Andrew Carey Ruffhead in Survey review, vol 48 n° 350 (September 2016)
[article]
Titre : The SMITSWAM method of datum transformations consisting of Standard Molodensky in two stages with applied misclosures Type de document : Article/Communication Auteurs : Andrew Carey Ruffhead, Auteur Année de publication : 2016 Article en page(s) : pp 376 - 384 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] approximation
[Termes IGN] ellipsoïde (géodésie)
[Termes IGN] transformation de coordonnéesRésumé : (auteur) For three-parameter datum transformations to be applied rigorously, geodetic coordinates on the first ellipsoid need to be converted to Cartesian coordinates before application of the shifts, then converted to geodetic coordinates on the second ellipsoid. The Standard Molodensky method of datum transformation is more direct but is inexact. It also fails to reproduce the original coordinates when applied forward and back. However, this paper shows a pattern of proportionality between the misclosures and the errors in the forward approximations. This gives rise to a new method of computing the transformations, best described as “Standard Molodensky in two stages with applied misclosures” (SMITSWAM). The method is shown to be more than 1600 times more accurate than Standard Molodensky, coming close to the accuracy of the rigorous approach. SMITSWAM is also shown to be around 48% faster than the traditional form of the rigorous method which uses iteration. Numéro de notice : A2016-643 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1191748 En ligne : https://doi.org/10.1080/00396265.2016.1191748 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81848
in Survey review > vol 48 n° 350 (September 2016) . - pp 376 - 384[article]Use of the gyrotheodolite in underground networks of long high-speed railway tunnels / J. Velasco-Gómez, in Survey review, vol 48 n° 350 (September 2016)
[article]
Titre : Use of the gyrotheodolite in underground networks of long high-speed railway tunnels Type de document : Article/Communication Auteurs : J. Velasco-Gómez,, Auteur ; J. F. Prieto, Auteur ; I. Molina, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 329 - 337 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] déviation de la verticale
[Termes IGN] Espagne
[Termes IGN] géoïde
[Termes IGN] guidage de forage
[Termes IGN] guidage de véhicules
[Termes IGN] gyrothéodolite
[Termes IGN] lever souterrain
[Termes IGN] tunnel
[Termes IGN] voie ferréeRésumé : (auteur) The quality of geodetic networks for guiding Tunnel Boring Machines (TBMs) inside long tunnels depends largely on the correct use of a gyroscope. These networks are based on a series of control points at the tunnel entrance, and link each station by means of survey observations as they advance along the tunnel. Once, the networks are used to guide the TBM, they are no longer checked again. It is necessary to perform high accuracy astronomical observations to stars in order to determine the gyrotheodolite constant. Since astronomical observations cannot be made inside tunnels, geodetic azimuths have to be used for the computations. However, these azimuths cannot theoretically be compared with the astronomical azimuths obtained by the gyrotheodolite. An alternative is to compute the instrument constant using the values of the deviation of the vertical derived from a geoid model. That is the approach used in this work where a methodology for the design of underground networks in long tunnels is also presented. This procedure has been implemented during the construction of the Guadarrama and Pajares high-speed railway tunnels (Spain). Numéro de notice : A2016-640 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000043 En ligne : https://doi.org/10.1179/1752270615Y.0000000043 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81845
in Survey review > vol 48 n° 350 (September 2016) . - pp 329 - 337[article]A spatial analysis of GEOID03 and GEOID09 in Connecticut / Kazi Arifuzzaman in Journal of applied geodesy, vol 10 n° 2 (June 2016)PermalinkHigh-precision positioning of radar scatterers / Prabu Dheenathayalan in Journal of geodesy, vol 90 n° 5 (May 2016)PermalinkThe Canadian Geodetic Vertical Datum of 2013 (CGVD2013) / Marc Véronneau in Geomatica, vol 70 n° 1 (March 2016)PermalinkContribution of mass density heterogeneities to the quasigeoid-to-geoid separation / Robert Tenzer in Journal of geodesy, vol 90 n° 1 (January 2016)PermalinkPermalinkEléments de géodésie et de la théorie des moindres carrés / Abdelmajid Ben Hadj Salem (février 2016)PermalinkLes grands arcs de méridien du XIXème [dix-neuvième] siècle et la forme de la Terre / James Lequeux in XYZ, n° 145 (décembre 2015 - février 2016)PermalinkGravity field modelling and gravimetry / Jan Krynski in Geodesy and cartography, vol 64 n° 2 (December 2015)PermalinkOn the deformation analysis of point fields / Hiddo Velsink in Journal of geodesy, vol 89 n° 11 (november 2015)PermalinkA surface spherical harmonic expansion of gravity anomalies on the ellipsoid / S.J. Claessens in Journal of geodesy, vol 89 n° 10 (october 2015)Permalink