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Estimation of tropospheric wet refractivity using tomography method and artificial neural networks in Iranian case study / Mir Reza Ghaffari Razin in GPS solutions, Vol 24 n° 3 (July 2020)  

Public [article]  inGPS solutions > Vol 24 n° 3 (July 2020) Titre : Estimation of tropospheric wet refractivity using tomography method and artificial neural networks in Iranian case study Type de document : Article/Communication Auteurs : Mir Reza Ghaffari Razin, Auteur ; Behzad Voosoghi, Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] coefficient de corrélation [Termes IGN] données GPS [Termes IGN] erreur moyenne quadratique [Termes IGN] erreur relative [Termes IGN] Iran [Termes IGN] réfraction atmosphérique [Termes IGN] réseau neuronal artificiel [Termes IGN] retard troposphérique [Termes IGN] retard troposphérique zénithal [Termes IGN] tomographie par GPS [Termes IGN] vapeur d'eau [Termes IGN] voxel Résumé : (auteur) Using the observations from local and regional GPS networks, the estimation of slant wet delays (SWDs) is possible for each line of sight between satellite and receiver. The observations of SWD are used to model horizontal and vertical variations of the wet refractivity in the atmosphere above the study area. This work is done using the tomography method. In tomography, the horizontal variations of tropospheric wet refractivity are modeled with the polynomial in degree and rank of 2 with latitude and longitude as variables. Also, altitude variations are modeled in the form of discrete layers with constant heights. The main innovation is to estimate the tropospheric parameters for each line of sight by the artificial neural networks (ANNs). The SWD obtained from GPS observations for the different signals at each station is compared with the SWD generated by the ANNs (SWDGPS–SWDANNs). The square of the difference between these two values is introduced as the cost function in the ANNs. To evaluate, we used observations from October 27 to 31, 2011. The availability of GPS and radiosonde data is the main reason for choosing this timeframe. The correlation coefficient, root mean square error (RMSE), and relative error allow for evaluation of the proposed model. The results were also compared with the results of the voxel-based troposphere tomography method. For a more detailed evaluation, four test stations are selected and ANN zenith wet delays (ZWDANN) are compared with the ZWDGPS. Observations of test stations are not used in the modeling step. The correlation coefficient in the testing step for TomoANN and Tomovoxel is 0.9006 and 0.8863, respectively. The mean RMSE at 5 days for TomoANN and Tomovoxel is calculated as 0.63 and 0.71 mm/km, respectively. Also, the average relative error at the four test stations for TomoANN is 15.37% and for Tomovoxel it is 19.69%. The results demonstrate the better capability of the proposed method in the modeling of the tropospheric wet refractivity in the region of Iran. Numéro de notice : A2020-238 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-00979-y Date de publication en ligne : 10/04/2020 En ligne : https://doi.org/10.1007/s10291-020-00979-y Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94986 [article]

Génération d'observations pour la validation ou la comparaison de logiciels d'ajustement de mesures par moindres carrés / Stéphane Durand in XYZ, n° 157 (décembre 2018 - février 2019)

Public [article]  inXYZ > n° 157 (décembre 2018 - février 2019) . - pp 37 - 44 Titre : Génération d'observations pour la validation ou la comparaison de logiciels d'ajustement de mesures par moindres carrés Type de document : Article/Communication Auteurs : Stéphane Durand, Auteur Année de publication : 2018 Article en page(s) : pp 37 - 44 Note générale : bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Topographie [Termes IGN] analyse comparative [Termes IGN] compensation par moindres carrés [Termes IGN] erreur relative [Termes IGN] estimateur [Termes IGN] test de performance [Termes IGN] variance Résumé : (auteur) In a previous paper, published in 2012 in this journal we conducted comparison between the CoMet software and others least squares network adjustment applications in order to validate the ComeT application. To perform such comparisons, we generated several sets of measurements in networks sharing the same geometry but different side lengths, and compared the obtainedresults in terms of adjusted coordinates and estimated variance factor. The purpose of this contribution is to review and discuss some common methods used for generating observations and to present in more detail our method, the one used in the previous article, which present some specific properties. Numéro de notice : A2018-533 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91578 [article]

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112-2018041	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Seeing the light: a vision-aided integrity for precision relative navigation systems / Sean Calhoun in GPS world, vol 26 n° 7 (July 2015)  

Public [article]  inGPS world > vol 26 n° 7 (July 2015) . - pp 44 - 49 Titre : Seeing the light: a vision-aided integrity for precision relative navigation systems Type de document : Article/Communication Auteurs : Sean Calhoun, Auteur ; John Raquet, Auteur ; Gilbert L. Peterson, Auteur Année de publication : 2015 Article en page(s) : pp 44 - 49 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] capteur aérien [Termes IGN] erreur relative [Termes IGN] GNSS assisté pour la navigation [Termes IGN] navigation aérienne [Termes IGN] positionnement par GPS [Termes IGN] précision du positionnement [Termes IGN] véhicule aérien Résumé : (Editeur) In this month’s column, we’ll take a look at the development of a generalized vision-aided integrity monitor for precision relative navigation applications. The work is based on the concept of using a single-camera vision system, such as a visible-light or infrared electro-optical sensor, to monitor the occurrence of unacceptably large and potentially unsafe relative navigation errors. A vision-aided integrity monitor of this type could be extremely valuable in augmenting existing precision relative navigation systems, such as GPS, for many different safety-critical aerospace applications such as formation flying, aerial refueling, rendezvous/docking systems, and even precision landing. Numéro de notice : A2015-309 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : sans En ligne : http://gpsworld.com/innovation-seeing-the-light/ Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76534 [article]

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
067-2015071	RAB	Revue	Centre de documentation	En réserve L003	Disponible

A comparison of four common atmospheric correction methods / A.S. Mahiny in Photogrammetric Engineering & Remote Sensing, PERS, vol 73 n° 4 (April 2007)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 73 n° 4 (April 2007) . - pp 361 - 368 Titre : A comparison of four common atmospheric correction methods Type de document : Article/Communication Auteurs : A.S. Mahiny, Auteur ; B. Turner, Auteur Année de publication : 2007 Article en page(s) : pp 361 - 368 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] analyse comparative [Termes IGN] correction atmosphérique [Termes IGN] détection de changement [Termes IGN] erreur absolue [Termes IGN] erreur relative [Termes IGN] image Landsat-TM Résumé : (Auteur) Four atmospheric correction methods, two relative and two absolute, were compared in this study. Two of the methods (PIF and RCS) were relative approaches; COST is an absolute image-based method and 6S, an absolute modeling method. The methods were applied to the hazy bands 1 through 4 of a Landsat TM scene of the year 1997, which was being used in a change detection project. The effects of corrections were studied in woodland patches. Three criteria, namely (a) image attributes; (b) image classification results, and (c) landscape metrics, were used for comparing the performance of the correction methods. Average pixel values, dynamic range, and coefficient of variation of bands constituted the first criterion, the area of detected vegetation through image classification was the second criterion, and patch and landscape measures of vegetation the third criterion. Overall, the COST, RCS, and 6S methods performed better than PIF and showed more stable results. The 6S method produced some negative values in bands 2 through 4 due to the unavailability of some data needed in the model. Having to use only a single set of image pixels for normalization in the PIF method and the difficulty of selecting such samples in the study area may be the reasons for its poor performance. Copyright ASPRS Numéro de notice : A2007-140 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.73.4.361 En ligne : https://doi.org/10.14358/PERS.73.4.361 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28503 [article]

Quality assessment of SRTM C- and X-band interferometric data: Implications for the retrieval of vegetation canopy height / W.S. Walker in Remote sensing of environment, vol 106 n° 4 (28/02/2007)  

Public [article]  inRemote sensing of environment > vol 106 n° 4 (28/02/2007) . - pp 428 - 448 Titre : Quality assessment of SRTM C- and X-band interferometric data: Implications for the retrieval of vegetation canopy height Type de document : Article/Communication Auteurs : W.S. Walker, Auteur ; J.M. Kellndorfer, Auteur ; L.E. Pierce, Auteur Année de publication : 2007 Article en page(s) : pp 428 - 448 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] bande C [Termes IGN] bande X [Termes IGN] bruit (théorie du signal) [Termes IGN] canopée [Termes IGN] erreur de mesure [Termes IGN] erreur relative [Termes IGN] Etats-Unis [Termes IGN] filtrage du bruit [Termes IGN] hauteur des arbres [Termes IGN] image SRTM [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] MNS SRTM [Termes IGN] modèle numérique de surface [Termes IGN] qualité des données [Termes IGN] radargrammétrie Résumé : (Auteur) The Shuttle Radar Topography Mission distinguished itself as the first near-global spaceborne mission to demonstrate direct sensitivity to vertical vegetation structure. Whether this sensitivity is viewed as exploitable signal or unwanted bias, a great deal of interest exists in retrieving vegetation canopy height information from the SRTM data. This study presents a comprehensive application-specific assessment of SRTM data quality, focusing on the characterization and mitigation of two primary sources of relative vertical error: uncompensated Shuttle mast motion and random phase noise. The assessment spans four test sites located in the upper Midwestern United States and examines the dependence of data quality on both frequency, i.e., C-band vs. X-band, and the number of acquired datatakes. The results indicate that the quality of SRTM data may be higher than previously thought. Novel mitigation strategies include a knowledge-based approach to sample averaging, which has the potential to reduce phase noise error by 43 to 80%. The strategies presented here are being implemented as part of an ongoing effort to produce regional- to continental-scale estimates of vegetation canopy height within the conterminous U.S. Copyright Elsevier Numéro de notice : A2007-068 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2006.09.007 En ligne : https://doi.org/10.1016/j.rse.2006.09.007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28433 [article]

Analyse et analyse numérique / Luc Jolivet (2005)

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Status of the SRTM data processing: when will the world-wild 30m DTM data be available? / M. Werner in GIS Geo-Informations-Systeme, vol 2001 n° 12 (Dezember 2001)

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