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A phase space reconstruction based single channel ICA algorithm and its application in dam deformation analysis / W. Dai in Survey review, vol 47 n° 345 (November 2015)  

Public [article]  inSurvey review > vol 47 n° 345 (November 2015) . - pp 387 - 396 Titre : A phase space reconstruction based single channel ICA algorithm and its application in dam deformation analysis Type de document : Article/Communication Auteurs : W. Dai, Auteur ; D. Huang, Auteur ; B. Liu, Auteur Année de publication : 2015 Article en page(s) : pp 387 - 396 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie moderne [Termes IGN] analyse en composantes indépendantes [Termes IGN] barrage [Termes IGN] filtrage du bruit [Termes IGN] modèle de régression [Termes IGN] niveau de l'eau [Termes IGN] surveillance d'ouvrage [Termes IGN] température Résumé : (auteur) Separating noise, systematic errors and deformation components that are caused by different forces such as water pressure and temperature should be identified from dam deformation monitoring data to facilitate effective dam deformation analysis and consequently determine the potential dam structural damage. As source signals are assumed to be mutually independent, independent component analysis (ICA) can be used to separate the source signals from their mixtures. In addition to signal independence, another requirement of ICA theory is that the number of mixtures should not be less than that of source signals. Unfortunately, in most cases of dam deformation monitoring, only a single channel of observed displacement data is available for each monitoring point. Therefore, ICA with single channel data input (called single channel ICA) is necessary in the application of deformation analysis. In this paper, we apply a phase space reconstruction based single channel ICA (PSR-ICA) algorithm to de-noise deformation monitoring data and separate deformation components introduced by different forces from these de-noised data. A numerical simulation is conducted, and results indicate that PSR-ICA is an efficient tool not only for denoising data but also for separating deformation components caused by different forces. PSR-ICA is then further utilised to process the displacement monitoring data of Wuqiangxi Dam. Results indicate that the two extracted main displacement components are nearly consistent with the displacement components; temperature and water level are used as variables and are computed by using a regression model. Both numerical simulated and real life dams demonstrate that PSR-ICA is an effective tool for separating deformation components by different causative forces and is therefore beneficial to dam deformation analysis. Numéro de notice : A2015-945 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000139 En ligne : https://doi.org/10.1179/1752270614Y.0000000139 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79649 [article]

Extendable linearised adjustment model for deformation analysis / Hiddo Velsink in Survey review, vol 47 n° 345 (November 2015)  

Public [article]  inSurvey review > vol 47 n° 345 (November 2015) . - pp 397 - 410 Titre : Extendable linearised adjustment model for deformation analysis Type de document : Article/Communication Auteurs : Hiddo Velsink, Auteur Année de publication : 2015 Article en page(s) : pp 397 - 410 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie moderne [Termes IGN] ajustement de paramètres [Termes IGN] analyse diachronique [Termes IGN] congruence [Termes IGN] matrice de covariance [Termes IGN] surveillance d'ouvrage [Termes IGN] tachéomètre électronique [Termes IGN] transformation affine Résumé : (auteur) This paper gives a linearised adjustment model for the affine, similarity and congruence transformations in 3D that is easily extendable with other parameters to describe deformations. The model considers all coordinates stochastic. Full positive semi-definite covariance matrices and correlation between epochs can be handled. The determination of transformation parameters between two or more coordinate sets, determined by geodetic monitoring measurements, can be handled as a least squares adjustment problem. It can be solved without linearisation of the functional model, if it concerns an affine, similarity or congruence transformation in one-, two- or three-dimensional space. If the functional model describes more than such a transformation, it is hardly ever possible to find a direct solution for the transformation parameters. Linearisation of the functional model and applying least squares formulas is then an appropriate mode of working. The adjustment model is given as a model of observation equations with constraints on the parameters. The starting point is the affine transformation, whose parameters are constrained to get the parameters of the similarity or congruence transformation. In this way the use of Euler angles is avoided. Because the model is linearised, iteration is necessary to get the final solution. In each iteration step approximate coordinates are necessary that fulfil the constraints. For the affine transformation it is easy to get approximate coordinates. For the similarity and congruence transformation the approximate coordinates have to comply to constraints. To achieve this, use is made of the singular value decomposition of the rotation matrix. To show the effectiveness of the proposed adjustment model total station measurements in two epochs of monitored buildings are analysed. Coordinate sets with full, rank deficient covariance matrices are determined from the measurements and adjusted with the proposed model. Testing the adjustment for deformations results in detection of the simulated deformations. Numéro de notice : A2015-946 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000140 En ligne : https://doi.org/10.1179/1752270614Y.0000000140 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79650 [article]

Establishment of new Oman National Geodetic Datum ONGD14 / Y. Al-Toobi in Survey review, vol 47 n° 345 (November 2015)  

Public [article]  inSurvey review > vol 47 n° 345 (November 2015) . - pp 418 - 428 Titre : Establishment of new Oman National Geodetic Datum ONGD14 Type de document : Article/Communication Auteurs : Y. Al-Toobi, Auteur ; S. Al-Hashmi, Auteur ; B. Al-Busaidi, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 418 - 428 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] Bernese [Termes IGN] international GPS service for geodynamics [Termes IGN] Oman [Termes IGN] Oman National Geodetic Datum [Termes IGN] station GPS [Termes IGN] système de référence local Résumé : (auteur) The main objective of enhancing national geodetic control is to create a homogenous horizontal survey control for the country. The realisation of a new geocentric datum, namely the Oman National Geodetic Datum (ONGD14), provides the GPS user community with a modern surveying infrastructure. The existing national geodetic control will be strengthened through the enhancement of the old control network and the future establishment of GPS Oman National CORS Network stations. A dedicated project has been initiated by the National Survey Authority of Oman for the establishment of ONGD14. The first task involves checking the quality of the existing geodetic network of first and second order GPS control stations. This was then followed by carrying out a longer GPS geodetic measurement campaign involving 20 existing control stations throughout the country. GPS processing for precise baselines computation using Bernese software has been carried out. In realising the ONGD14, a network of 20 occupied control stations was connected to almost 50 IGS sites in the vicinity of Oman. A nation-wide combined network adjustment of common station coordinates in latest solution of ITRF2008 frame epoch 2013 (ITRF2008@2013) was then performed to establish the ONGD14. Numéro de notice : A2015-913 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270614Y.0000000143 En ligne : https://doi.org/10.1179/1752270614Y.0000000143 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79651 [article]

Data quality assessment and the positioning performance analysis of BeiDou in Hong Kong / Y. Xu in Survey review, vol 47 n° 345 (November 2015)  

Public [article]  inSurvey review > vol 47 n° 345 (November 2015) . - pp 446 - 457 Titre : Data quality assessment and the positioning performance analysis of BeiDou in Hong Kong Type de document : Article/Communication Auteurs : Y. Xu, Auteur ; S. Ji, Auteur Année de publication : 2015 Article en page(s) : pp 446 - 457 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] mesurage de phase [Termes IGN] positionnement différentiel [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] précision du positionnement [Termes IGN] signal BeiDou [Termes IGN] test de performance Résumé : (auteur) As the satellite constellation, frequency structure, time and coordinate reference system of the Chinese BeiDou are all different from those of GPS, the quality of observations is also supposed to be different from GPS. At the same time, the positioning performance of the GPS and BeiDou combined system should be much better in view of the availability of more visible satellites. The purpose of this paper is to assess the quality of BeiDou pseudorange and carrier phase observation, and to compare the performance of GPS, BeiDou and the combined system in terms of availability, integrity and positioning accuracy with practical data in Hong Kong. The experiment results showed that the noise and multipath of GEOs (geostationary earth orbit satellites) pseudorange measurement fluctuates within 1.5 m, while the variations of IGSOs (geostationary earth orbit inclined geosynchronous orbit satellites) and MEOs (medium earth orbit satellites) are more obvious. The amplitudes of the triple-carrier combination of time series of GEOs, IGSOs and MEOs carrier phase measurements are 4, 6, and 6 mm, respectively. In addition, the absolute and relative positioning precision of BeiDou is very similar to that of GPS, and the performance of the combined systems is best. Numéro de notice : A2015-914 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000005 En ligne : https://doi.org/10.1179/1752270615Y.0000000005 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79652 [article]