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Auteur T. Wunderlich |
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Target identification in terrestrial laser scanning / Xuming Ge in Survey review, vol 47 n° 341 (March 2015)
[article]
Titre : Target identification in terrestrial laser scanning Type de document : Article/Communication Auteurs : Xuming Ge, Auteur ; T. Wunderlich, Auteur Année de publication : 2015 Article en page(s) : pp 129 - 140 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] chaîne de traitement
[Termes IGN] détection de cible
[Termes IGN] télémètre laser à balayage
[Termes IGN] télémétrie laser terrestreRésumé : (auteur) Target identification is an important process in terrestrial laser scanner (TLS) measurements; however, due to strong competition between manufacturers, the design of laser scanners is kept secret and is usually strengthened by accompanying proprietary software. Moreover, the target identification algorithms (i.e. definitions of the target centre) are not specified. This makes it difficult for users to objectively compare scanners from different manufacturers and to judge the reliability of the captured scan data by a brand scanner and accompanying software. This paper presents a unified general method to complete the process of target identification. The proposed method consists of four major steps: first, determination of the target plane; second, classification of the reflection intensity values and extraction of the border between white and black; third, detection and elimination of erroneous points from step two; and fourth, fitting of the intersection lines and calculation of the centre of the two lines. Because TLS is a reflectorless surveying model that can receive hundreds of signals, its measurements require more stringent objective conditions than traditional measurement by total stations (TS). Therefore, robust estimation methods are used to reduce the influence of random errors; moreover, the model of error-in-value (EIV) is also introduced to deal with captured data. Finally, the target’s centre can be obtained from an iteration process. For the experiments, a Leica HDS 7000 terrestrial laser scanner, with its accompanying software, Cyclone, and a Leica Laser Tracker AT901 were employed. The performance of the proposed method is compared with Cyclone and some early methods from published studies at different resolutions and distances. The paper concludes that the proposed method can obtain reliable results at the same level of accuracy level as those obtained using accompanying software; thus, it provides an objective means to compare the quality of different scanners. The advantage is that our method only makes use of information provided by all scanners and does not require additional proprietary information that cannot be accessed. Numéro de notice : A2015-959 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1179/1752270614Y.0000000097 En ligne : https://doi.org/10.1179/1752270614Y.0000000097 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79946
in Survey review > vol 47 n° 341 (March 2015) . - pp 129 - 140[article]Die voraussetzungsfreie Bestimmung von Refraktionswinkeln / T. Wunderlich (1985)
Titre : Die voraussetzungsfreie Bestimmung von Refraktionswinkeln Titre original : [La détermination sans condition préalable de l'angle de réfraction] Type de document : Monographie Auteurs : T. Wunderlich, Auteur Editeur : Vienne [Autriche] : Technische Universität Wien Année de publication : 1985 Collection : Geowissenschaftliche Mitteilungen, ISSN 1811-8380 num. 26 Importance : 193 p. Format : 21 x 30 cm Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Nivellement
[Termes IGN] altitude
[Termes IGN] distance zénithale
[Termes IGN] hauteur ellipsoïdale
[Termes IGN] méthode des moindres carrés
[Termes IGN] réfraction
[Termes IGN] réfraction atmosphériqueIndex. décimale : 30.50 Nivellement - généralités Résumé : (Auteur) This thesis describes the "Vertical Quadrangle Method” that has been developed in consequence of the "Vertical Triangle" of Sanchez. After preliminary determination of all spatial and zenith distances in the vertical quadrilateral (completed by its diagonals) with additional measurements of vertical deflections and precise levelling, the refraction angles can be derived from geometrical parameters exclusively. The method can only be applied in major differences of elevation (several 100 meters) and it claims extreme precision in the measurement of the spatial distances (md/d <= 1.10-6). The advantages of the method are that it requires none but the usual geodetic equipment and a simple mode of calculation including a rigorous theory of errors. The mean square error allotted to each refraction angle calculated, is derived from the mean square errors of the measured parameters according to the law of propagation of errors in correlated observations. The efficiency of the method has been proved by means of extensive series of measurements in a special testnetwork near Vienna (vertical quadrangle "Hohe Wand"). The required high standard of accuracy could be obtained with considerable dedication of time, instruments and personal efforts. The mean accuracy of the calculated angles of refraction was + 3cc. The mean square errors of the deducted large differences of elevation were less than 1 cm. As the zenith distances have been observed over 24 hours, fluctuations of the refraction angles during the day could be assessed and remarkable anomalies of refraction were detected. In particular the method may be applied to provide absolute refraction angles as a basis of comparison with refraction angles from meteorological models as especially in major differences of altitude the usual control by means of levelling is impracticable. The highly accurate linking of levelling lines in valleys with the vertical control network of mountain peaks is a further application of the method that justifies its expenditure. Numéro de notice : 55004 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=59743 Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 55004-01 30.50 Livre Centre de documentation Géodésie Disponible