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A mixed weighted least squares and weighted total least squares adjustment method and its geodetic applications / Y. Zhou in Survey review, vol 48 n° 351 (October 2016)  

Public [article]  inSurvey review > vol 48 n° 351 (October 2016) . - pp 421 - 429 Titre : A mixed weighted least squares and weighted total least squares adjustment method and its geodetic applications Type de document : Article/Communication Auteurs : Y. Zhou, Auteur ; X. Fang, Auteur Année de publication : 2016 Article en page(s) : pp 421 - 429 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie [Termes IGN] compensation par moindres carrés [Termes IGN] méthode des moindres carrés [Termes IGN] pondération [Termes IGN] variable Résumé : (Auteur) A mixed weighted least squares (WLS) and weighted total least squares (WTLS) (mixed WLS–WTLS) method is presented for an errors-in-variables (EIV) model with some fixed columns in the design matrix. The numerical computational scheme and an approximate accuracy assessment method are also provided. It is extended from the mixed Least squares (LS)–Total least squares (TLS) method to deal with the case that the random columns are corrupted by heteroscedastic correlated noises. The mixed WLS–WTLS method can improve the computational efficiency compared with the existing WTLS methods without loss of accuracy, particularly when the fixed columns are far more than random ones. The Bursa transformation and parallel lines fitting examples are carried out to demonstrate the performance of the proposed algorithm. Since the mixed WLS–WTLS problem includes both the WLS and the WTLS problem, it will have a more wide range of applications. Numéro de notice : A2016-823 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000040 En ligne : https://doi.org/10.1179/1752270615Y.0000000040 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82639 [article]

External error modelling with combined model in terrestrial laser scanning / J. Wang in Survey review, vol 48 n° 346 (January 2016)  

Public [article]  inSurvey review > vol 48 n° 346 (January 2016) . - pp 40 - 50 Titre : External error modelling with combined model in terrestrial laser scanning Type de document : Article/Communication Auteurs : J. Wang, Auteur ; H. Kutterer, Auteur ; X. Fang, Auteur Année de publication : 2016 Article en page(s) : pp 40 - 50 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] étalonnage de capteur (imagerie) [Termes IGN] itération [Termes IGN] modèle de Gauss-Helmert [Termes IGN] réfraction atmosphérique [Termes IGN] télémétrie laser sur satellite [Termes IGN] télémétrie laser terrestre Résumé : (auteur) Terrestrial laser scanning (TLS) is a promising tool in geodetic applications. Data quality of outdoor TLS measurements is considerably limited by external errors caused by atmospheric variations and object related factors. In this study, external models related to atmospheric refraction, beam wander and incidence angle were introduced and integrated into a seven-parameter similarity transformation (7PST) model to compose a combined model. The combined model was rigorously adjusted by an iterative Gauss–Helmert (GH) model primarily to estimate external calibration parameters and transformation parameters simultaneously. In the application on a dam surface, a t-test showed that a significant external calibration parameter was the range scale, which mainly corresponded with the incidence angle model. The precision of estimated representative points was improved by approximately 50% with the proposed method. The presented models show a great potential for detecting external errors and registering multiple scans in outdoor applications. Numéro de notice : A2016-045 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/00396265.2015.1097589 En ligne : https://doi.org/10.1080/00396265.2015.1097589 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79638 [article]

On the detection of systematic errors in terrestrial laser scanning data / J. Wang in Journal of applied geodesy, vol 6 n° 3-4 (November 2012)  

Public [article]  inJournal of applied geodesy > vol 6 n° 3-4 (November 2012) . - pp 187 - 192 Titre : On the detection of systematic errors in terrestrial laser scanning data Type de document : Article/Communication Auteurs : J. Wang, Auteur ; H. Kutterer, Auteur ; X. Fang, Auteur Année de publication : 2012 Article en page(s) : pp 187 - 192 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] algorithme ICP [Termes IGN] barrage [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] erreur systématique [Termes IGN] lasergrammétrie [Termes IGN] modèle de Gauss-Helmert [Termes IGN] segmentation d'image [Termes IGN] télémétrie laser sur satellite Résumé : (Auteur) Quality descriptions are parts of the key tasks of geodetic data processing. Systematic errors should be detected and avoided in order to insure the high quality standards required by structural monitoring. In this study, the iterative closest point (ICP) method was invested to detect systematic errors in two overlapping data sets. There are three steps to process the systematic errors: firstly, one of the data sets was transformed to a reference system by the introduction of the Gauss–Helmert (GH) model. Secondly, quadratic form estimation and segmentation methods are proposed to guarantee the overlapping data sets. Thirdly, the ICP method was employed for a finer registration and detecting the systematic errors. A case study was casted in which a dam surface in Germany was scanned by terrestrial laser scanning (TLS) technology. The results indicated that with the conjugation of ICP algorithm the accuracy of the data sets was improved approximately by 1.6 mm. Numéro de notice : A2012-598 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1515/jag-2012-0025 En ligne : http://www.degruyter.com/view/j/jag.2012.6.issue-3-4/jag-2012-0025/jag-2012-0025 [...] Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32044 [article]