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A new method to improve the performance of multi-GNSS pseudorange positioning in signal-degraded environment / Hui Liu in Advances in space research, vol 58 n° 4 (August 2016)
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Titre : A new method to improve the performance of multi-GNSS pseudorange positioning in signal-degraded environment Type de document : Article/Communication Auteurs : Hui Liu, Auteur ; Longwei Xu, Auteur ; Bao Shu, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 577 - 586 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] interopérabilité
[Termes IGN] mesurage de pseudo-distance
[Termes IGN] système de positionnement par satellites
[Termes IGN] visibilitéRésumé : (auteur) There are two existing multi-GNSS positioning methods, (1) separate receiver clock parameter is set for each constellation, (2) estimating intersystem biases (ISBs) in advance to obtain position solutions with only four unknowns. The former is the regular method and its unknowns include three receiver-coordinate parameters and several receiver clock parameters (depend on the number of participant constellations), so that it may disable when few satellites belonging to different GNSS are in view. The latter is one workable way to obtain position solution with only four visible satellites. In addition to the disabled regular method, the positioning results by the ISB-corrected method are often unsatisfactory for navigation users in signal-degraded environment. Both the deviation of ISB-solutions and the remaining measurement errors of the need corrected observations are factors to degrade location precision. Apart from these, fewer visible satellites usually cause a low robustness of the positioning model, which cause the negative influence of various errors is amplified. Based on the variation of various measurement errors, we propose a new ISSB-corrected method with observations corrected by corresponding satellite-dependent parameters. The new parameter contains the difference of time scales, hardware delays and uncorrected measurement errors between the corresponding satellite and reference, in other words, it can synthetically consider measurement errors and the ISB. By the ISSB-corrected method, we not only achieve positioning solutions with four satellites, but also significantly reduce the accuracy loss. Many experiments are conducted to present the superiority of the ISSB-corrected method. In open-area, the accuracies of regular and ISB-corrected methods are nearly equal. Apart from a similar accuracy in horizontal, the accuracy is improved by approximate 10% in up direction with respect to the two existing methods. Given the high redundancy of model in open-area, the new method may not improve the accuracy remarkably. However, it can make great contributions in signal-degraded environments. In order to compare the performance of ISB- and ISSB-corrected methods in environment with limited visible satellites, we simulate several scenarios (different satellites participant or various receivers) with only four participant satellites in the positioning solution. By the ISSB-corrected method, the 3D RMS of positioning results with four satellites is about 15 m, while it is usually worse than 25 m for the ISB-corrected method. In an urban vehicular test, the horizontal positioning error of the ISSB-corrected method is less than 20 m; and the ISB-corrected method may reach up to 70 m. Numéro de notice : A2016-592 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2016.05.016 En ligne : http://dx.doi.org/10.1016/j.asr.2016.05.016 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81748
in Advances in space research > vol 58 n° 4 (August 2016) . - pp 577 - 586[article]Allometric models for estimating tree volume and aboveground biomass in lowland forests of Tanzania / Wilson Ancelm Mugasha in International journal of forestry research, vol 2016 ([01/08/2016])
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Titre : Allometric models for estimating tree volume and aboveground biomass in lowland forests of Tanzania Type de document : Article/Communication Auteurs : Wilson Ancelm Mugasha, Auteur ; Ezekiel Edward Mwakalukwa, Auteur ; Emannuel Luoga, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : 13 p. Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation
[Termes IGN] allométrie
[Termes IGN] biomasse aérienne
[Termes IGN] densité du bois
[Termes IGN] modèle numérique
[Termes IGN] Tanzanie
[Termes IGN] volume en boisRésumé : (auteur) Models to assist management of lowland forests in Tanzania are in most cases lacking. Using a sample of 60 trees which were destructively harvested from both dry and wet lowland forests of Dindili in Morogoro Region (30 trees) and Rondo in Lindi Region (30 trees), respectively, this study developed site specific and general models for estimating total tree volume and aboveground biomass. Specifically the study developed (i) height-diameter (ht-dbh) models for trees found in the two sites, (ii) total, merchantable, and branches volume models, and (iii) total and sectional aboveground biomass models of trees found in the two study sites. The findings show that site specific ht-dbh model appears to be suitable in estimating tree height since the tree allometry was found to differ significantly between studied forests. The developed general volume models yielded unbiased mean prediction error and hence can adequately be applied to estimate tree volume in dry and wet lowland forests in Tanzania. General aboveground biomass model appears to yield biased estimates; hence, it is not suitable when accurate results are required. In this case, site specific biomass allometric models are recommended. Biomass allometric models which include basic wood density are highly recommended for improved estimates accuracy when such information is available. Numéro de notice : A2016--110 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1155/2016/8076271 En ligne : http://dx.doi.org/10.1155/2016/8076271 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84741
in International journal of forestry research > vol 2016 [01/08/2016] . - 13 p.[article]An immune genetic algorithm to buildings displacement in cartographic generalization / Yageng Sun in Transactions in GIS, vol 20 n° 4 (August 2016)
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Titre : An immune genetic algorithm to buildings displacement in cartographic generalization Type de document : Article/Communication Auteurs : Yageng Sun, Auteur ; Qingsheng Guo, Auteur ; Yuangang Liu, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 585 - 612 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme génétique
[Termes IGN] bâtiment
[Termes IGN] contrainte géométrique
[Termes IGN] contrainte relationnelle
[Termes IGN] déplacement d'objet géographique
[Termes IGN] généralisation automatique de données
[Termes IGN] généralisation cartographique
[Vedettes matières IGN] GénéralisationRésumé : (auteur) Spatial conflicts may occur when map data are displayed at a scale smaller than that of the source map. This study applies the displacement operator in cartographic generalization to resolve such spatial conflicts and to improve the clarity and legibility of map. The immune genetic algorithm (IGA) is used in this study for buildings displacement to solve conflicts. IGA is based on the genetic algorithm (GA) and employs the self-adjusting mechanism of antibody concentration to enhance population diversity. Meanwhile, the elitism retention strategy is adopted in IGA to guarantee that the best individual (antibody) is not lost and destroyed in the next generation to strengthen convergence efficiency. The compared experiment between IGA and GA shows that the displacement result produced by IGA performs better than GA. Finally, in order to make the displaced map more attractive to cartographers, two constraints – the building alignment constraint and building tangent relation constraint – are applied in IGA to restrict the buildings’ displacement. The same experimental data are adopted to prove that the improved IGA is useful for maintaining the two constraints. Numéro de notice : A2016--053 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/tgis.12165 En ligne : http://dx.doi.org/10.1111/tgis.12165 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83771
in Transactions in GIS > vol 20 n° 4 (August 2016) . - pp 585 - 612[article]Building displacement based on the topological structure / Yageng Sun in Cartographic journal (the), Vol 53 n° 3 (August 2016)
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Titre : Building displacement based on the topological structure Type de document : Article/Communication Auteurs : Yageng Sun, Auteur ; Qingsheng Guo, Auteur ; Yuangang Liu, Auteur ; et al., Auteur Année de publication : 2016 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme snake
[Termes IGN] déplacement d'objet géographique
[Termes IGN] généralisation automatique de données
[Termes IGN] optimisation (mathématiques)
[Termes IGN] partitionnement
[Termes IGN] pondération
[Termes IGN] relation spatiale
[Termes IGN] triangulation de Delaunay
[Vedettes matières IGN] GénéralisationRésumé : (auteur) Map data at smaller scales than their source can result in spatial conflict, whereby map symbols become too close, or overlaid. Server map generalisation operators may be applied to solve this problem, including displacement. In this paper, we show how an optimisation algorithm, the snake algorithm, was used to displace multiple objects in order to resolve spatial conflicts and maintain important spatial relationships between objects during displacement. Two principles based on the snake algorithm are proposed in this paper. First, the truss structure mirroring spatial proximity relationships between buildings and between building and road is formed based on the weighted proximity graph derived from constrained Delaunay triangulations (CDT) in each map partition. In the weighted proximity graph, each connecting line is determined as a snake and as an element unit to assemble the global stiffness matrix in snake algorithm. Second, a buffer method that calculates force between a building and a road (or other linear features) or between pair of buildings is adopted in the snake algorithm. This avoids the imbalance phenomenon caused by different force calculation methods during the displacement. The feasibility of the approach is demonstrated in obtaining real geographic data. Finally, the results are cartographically usable and in particular, the spatial relationships between objects are preserved. Numéro de notice : A2016-680 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1179/1743277414Y.0000000089 En ligne : http://dx.doi.org/10.1179/1743277414Y.0000000089 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81937
in Cartographic journal (the) > Vol 53 n° 3 (August 2016)[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 030-2016031 RAB Revue Centre de documentation En réserve L003 Disponible Disaggregation of remotely sensed soil moisture in heterogeneous landscapes using holistic structure-based models / Subit Chakrabarti in IEEE Transactions on geoscience and remote sensing, vol 54 n° 8 (August 2016)
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Titre : Disaggregation of remotely sensed soil moisture in heterogeneous landscapes using holistic structure-based models Type de document : Article/Communication Auteurs : Subit Chakrabarti, Auteur ; Jasmeet Judge, Auteur ; Tara Bongiovanni, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 4629 - 4641 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] algorithme d'apprentissage
[Termes IGN] cultures
[Termes IGN] désagrégation
[Termes IGN] Floride (Etats-Unis)
[Termes IGN] humidité du sol
[Termes IGN] modèle de régressionRésumé : (Auteur) In this paper, a novel machine learning algorithm is presented for disaggregation of satellite soil moisture (SM) based on self-regularized regressive models (SRRMs) using high-resolution correlated information from auxiliary sources. It includes regularized clustering that assigns soft memberships to each pixel at a fine scale followed by a kernel regression that computes the value of the desired variable at all pixels. Coarse-scale remotely sensed SM was disaggregated from 10 to 1 km using land cover (LC), precipitation, land surface temperature, leaf area index, and in situ observations of SM. This algorithm was evaluated using multiscale synthetic observations in NC Florida for heterogeneous agricultural LCs. It was found that the rmse for 96% of the pixels was less than 0.02 m 3/m3. The clusters generated represented the data well and reduced the rmse by up to 40% during periods of high heterogeneity in LC and meteorological conditions. The Kullback-Leibler divergence (KLD) between the true SM and the disaggregated estimates is close to zero, for both vegetated and bare-soil LCs. The disaggregated estimates were compared with those generated by the principle of relevant information (PRI) method. The rmse for the PRI disaggregated estimates is higher than the rmse for the SRRM on each day of the season. The KLD of the disaggregated estimates generated by the SRRM is at least four orders of magnitude lower than those for the PRI disaggregated estimates, whereas the computational time needed was reduced by three times. The results indicate that the SRRM can be used for disaggregating SM with complex nonlinear correlations on a grid with high accuracy. Numéro de notice : A2016-888 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2016.2547389 En ligne : http://dx.doi.org/10.1109/TGRS.2016.2547389 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83068
in IEEE Transactions on geoscience and remote sensing > vol 54 n° 8 (August 2016) . - pp 4629 - 4641[article]Estimation of satellite antenna phase center offsets for Galileo / Peter Steigenberger in Journal of geodesy, vol 90 n° 8 (August 2016)
PermalinkA geometry-free and ionosphere-free multipath mitigation method for BDS three-frequency ambiguity resolution / Dezhong Chen in Journal of geodesy, vol 90 n° 8 (August 2016)
PermalinkGround-based phase wind-up and its application in yaw angle determination / M. Cai in Journal of geodesy, vol 90 n° 8 (August 2016)
PermalinkA local structure and direction-aware optimization approach for three-dimensional tree modeling / Zhen Wang in IEEE Transactions on geoscience and remote sensing, vol 54 n° 8 (August 2016)
PermalinkA new computerized ionosphere tomography model using the mapping function and an application to the study of seismic-ionosphere disturbance / Jian Kong in Journal of geodesy, vol 90 n° 8 (August 2016)
PermalinkA spatial data infrastructure approach for the characterization of New Zealand's groundwater systems / Alexander Kmoch in Transactions in GIS, vol 20 n° 4 (August 2016)
PermalinkThe international GNSS monitoring and assessment service in a multi-system environment / Echoda Ngbede Joshua Ada in Inside GNSS, vol 11 n° 4 (July - August 2016)
PermalinkApplication of satellite navigation system for emergency warning and alerting / Suelynn Choy in Computers, Environment and Urban Systems, vol 58 (July 2016)
PermalinkAssessment of orthoimage and DEM derived from ZY-3 stereo image in Northeastern China / Y. Dong in Survey review, vol 48 n° 349 (July 2016)
PermalinkA comparative analysis of measurement noise and multipath for four constellations: GPS, BeiDou, GLONASS and Galileo / Changsheng Cai in Survey review, vol 48 n° 349 (July 2016)
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