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Auteur W. Cheng |
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Assessment of orthoimage and DEM derived from ZY-3 stereo image in Northeastern China / Y. Dong in Survey review, vol 48 n° 349 (July 2016)
[article]
Titre : Assessment of orthoimage and DEM derived from ZY-3 stereo image in Northeastern China Type de document : Article/Communication Auteurs : Y. Dong, Auteur ; W. Cheng, Auteur ; Hoon Chang, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 258 - 268 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] Chine
[Termes IGN] image ZiYuan-3
[Termes IGN] MNS ASTER
[Termes IGN] modèle numérique de surface
[Termes IGN] modèle par fonctions rationnelles
[Termes IGN] modèle stéréoscopique
[Termes IGN] orthoimageRésumé : (auteur) ZiYuan-3 (ZY-3, meaning Resource-3) is China's first civilian multispectral satellite with high-resolution stereo mapping capability. The along-track stereo images of ZY-3 allow the generation of digital elevation models (DEMs) for various mapping applications. This article evaluated the precision of the derived stereo DEM and orthoimages of ZY-3 data for a test site in Northeastern China. Pixel offset and GPS survey data were used to evaluate the image products. Orthoimages were derived by incorporating rational polynomial coefficients (RPCs) of the satellite orbits and the reference DEMs, including the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) global digital elevation model (GDEM) and ZY-3 stereo elevation model. The generations of orthoimages were categorised into four approaches depending on the RPCs, control points and/or reference DEMs used. When only the ASTER GDEM was used, the derived orthoimages of the forward and backward viewing sensors showed clear pixel offsets against the GPS check points (CKPs). For example, the offsets of the orthoimage derived using forward-looking image were 13·58 and 26·50 m, in x (easting) and y (northing) directions, respectively. These results also indicated that the pixel offset vectors between the forward and backward orthoimages was systematic which was caused by the error in the RPCs. The second and third approaches were to generate the ZY-3 stereo DEMs first, with and without the use of ground control points (GCPs), and then used the stereo DEMs to generate the orthoimages of the forward and backward looking images. The forth approach used both GCPs and ASTER GDEM to generate the orthoimages. The results showed the use of four GCPs in the process improved the accuracy of the orthoimages. Therefore, ZY-3 can deliver the DEM and orthoimage products to meet the accuracy requirement of the national 1 : 50 000 mapping with four well distributed GCPs. Numéro de notice : A2016-623 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1179/1752270615Y.0000000027 En ligne : https://doi.org/10.1179/1752270615Y.0000000027 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81825
in Survey review > vol 48 n° 349 (July 2016) . - pp 258 - 268[article]Real-time adjustment underwater positioning system for submarines / W. Cheng in Marine geodesy, vol 33 n° 2-3 (April - September 2010)
[article]
Titre : Real-time adjustment underwater positioning system for submarines Type de document : Article/Communication Auteurs : W. Cheng, Auteur ; J. Jhou, Auteur Année de publication : 2010 Article en page(s) : pp 117 - 134 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] compensation
[Termes IGN] ligne de base
[Termes IGN] modèle géométrique
[Termes IGN] modèle numérique de terrain
[Termes IGN] onde acoustique
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] relief sous-marin
[Termes IGN] sous-marin
[Termes IGN] temps réel
[Termes IGN] traitement automatique de données
[Termes IGN] vitesseRésumé : (Auteur) A rapid real-time adjustment scheme is proposed for improving the precision of the conventional short-base line (SBL) positioning fix system used by submarines and other underwater vehicles. In the proposed approach, an initial position estimate is obtained by solving the conventional SBL tracking equations of the submarine given the assumptions of a constant speed of sound in water and a straight-line propagation path. In the first stage of the real-time adjustment procedure, this initial estimate is corrected using an iterative computation scheme based on a 3D geometry model. The improved position estimate is then used to compute a new, more accurate value of the speed of sound in water. Finally, in the second stage of the real-time adjustment procedure, the corrected speed of sound in water and the discrepancy between the original and corrected position estimates obtained in the first adjustment procedure are applied to update the coordinates of the submarine based on the second signal received from the pinger. The numerical results show that the proposed real-time adjustment system yields a significant improvement in the accuracy of the positioning fix estimates compared to those obtained from the conventional SBL method or the SBL method with the first adjustment procedure only. Numéro de notice : A2010-555 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2010.492279 Date de publication en ligne : 16/05/2011 En ligne : https://doi.org/10.1080/01490419.2010.492279 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30747
in Marine geodesy > vol 33 n° 2-3 (April - September 2010) . - pp 117 - 134[article]Réservation
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