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Evaluating the use of GPS heights in water conservation applications / Ahmed F. Elaksher in Survey review, vol 48 n° 348 (May 2016)
[article]
Titre : Evaluating the use of GPS heights in water conservation applications Type de document : Article/Communication Auteurs : Ahmed F. Elaksher, Auteur ; A. Fernald, Auteur ; F. Kapoko, Auteur Année de publication : 2016 Article en page(s) : pp 195 - 201 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie
[Termes IGN] altitude orthométrique
[Termes IGN] analyse comparative
[Termes IGN] GPS en mode statique
[Termes IGN] hauteur ellipsoïdale
[Termes IGN] niveau de l'eau
[Termes IGN] nivellement indirect
[Termes IGN] Nouveau-Mexique (Etats-Unis)
[Termes IGN] positionnement par GPS
[Termes IGN] positionnement statique rapide
[Termes IGN] récepteur GPS
[Termes IGN] station de contrôle
[Termes IGN] station de référenceRésumé : (auteur) Accurate water level elevations are imperative for water resource management. This paper presents the outcomes of a research study using GPS in measuring water level heights. The authors observed the water elevations of several wells, United States Geological Survey (USGS) gauges and acequia points at three different locations in North–Central New Mexico, USA. Different rapid static and static observation sessions were collected independently and adjusted using the nearby reference control stations. The authors used two different sets of receivers: four Topcon Hiper Lite+ and two Leica GPS1200 The authors were able to examine several network configurations with different continuously operating reference station (CORS) stations. Our findings were analogous to empirically expected errors and showed insignificant differences among the heights obtained from rapid static and static sessions at a 95% confidence level. The authors also compared the results with National Geodetic Survey online positioning users service (NGS OPUS) solutions and confirmed the accuracy of our measurements. As independent measurement technique, we measured the height differences among several of these points with conventional levelling surveys. Our GPS measurements provided small disagreements with height differences obtained with the terrestrial surveys, after the GPS heights were reduced to their orthometric correspondences. Based on these findings, current rapid static GPS positioning methodologies are capable of providing equivalent accuracies as those obtained by static GPS and ground surveying techniques. Numéro de notice : A2016-274 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000021 En ligne : http://doi.org/10.1179/1752270615Y.0000000021 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80829
in Survey review > vol 48 n° 348 (May 2016) . - pp 195 - 201[article]Potential of GPS common clock single-differences for deformation monitoring / Steffen Schön in Journal of applied geodesy, vol 10 n° 1 (March 2016)
[article]
Titre : Potential of GPS common clock single-differences for deformation monitoring Type de document : Article/Communication Auteurs : Steffen Schön, Auteur ; Hue Kiem Pham, Auteur ; Tobias Kersten, Auteur ; Julia Leute, Auteur ; Andreas Bauch, Auteur Année de publication : 2016 Article en page(s) : pp 45 - 52 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] déformation géométrique
[Termes IGN] hauteur ellipsoïdale
[Termes IGN] horloge
[Termes IGN] positionnement cinématique
[Termes IGN] récepteur GNSS
[Termes IGN] simple différence
[Vedettes matières IGN] Traitement de données GNSSRésumé : (auteur) Global satellite navigation systems (GNSS) are a standard measurement device for deformation monitoring. In many applications, double-differences are used to reduce distance dependent systematic effects, as well as to eliminate the receiver and satellites clock errors. However, due to the navigation principle of one way ranging used in GPS, the geometry of the subsequent adjustment is weakened. As a result, the height component is generally determined three times less precisely than the horizontal coordinates. In addition, large correlations between the height and elevation dependent effects exist such as tropospheric refraction, mismodelled phase center variations, or multipath which restricts the attainable accuracy. However, for a kinematic analysis, i. e. for estimating high rate coordinate time series, the situation can be significantly improved if a common clock is connected to different GNSS receivers in a network or on a baseline. Consequently, between-station single-differences are sufficient to solve for the baseline coordinates. The positioning geometry is significantly improved which is reflected by a reduction of the standard deviation of kinematic heights by about a factor 3 underlining the benefits of this new approach. Real data from baselines at the Physikalisch-Technische Bundesanstalt campus at Braunschweig where receivers are connected over 290 m via an optical fiber link to a common clock was analysed. Numéro de notice : A2016-553 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2015-0029 En ligne : http://dx.doi.org/10.1515/jag-2015-0029 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81700
in Journal of applied geodesy > vol 10 n° 1 (March 2016) . - pp 45 - 52[article]Time series analysis of 3D coordinates using nonstochastic observations / Hiddo Velsink in Journal of applied geodesy, vol 10 n° 1 (March 2016)
[article]
Titre : Time series analysis of 3D coordinates using nonstochastic observations Type de document : Article/Communication Auteurs : Hiddo Velsink, Auteur Année de publication : 2016 Article en page(s) : pp 5 - 16 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] compensation de coordonnées
[Termes IGN] coordonnées cartésiennes
[Termes IGN] déformation géométrique
[Termes IGN] matrice de covariance
[Termes IGN] série temporelle
[Vedettes matières IGN] Traitement de données GNSSRésumé : (auteur) Adjustment and testing of a combination of stochastic and nonstochastic observations is applied to the deformation analysis of a time series of 3D coordinates. Nonstochastic observations are constant values that are treated as if they were observations. They are used to formulate constraints on the unknown parameters of the adjustment problem. Thus they describe deformation patterns. If deformation is absent, the epochs of the time series are supposed to be related via affine, similarity or congruence transformations. S-basis invariant testing of deformation patterns is treated. The model is experimentally validated by showing the procedure for a point set of 3D coordinates, determined from total station measurements during five epochs. The modelling of two patterns, the movement of just one point in several epochs, and of several points, is shown. Full, rank deficient covariance matrices of the 3D coordinates, resulting from free network adjustments of the total station measurements of each epoch, are used in the analysis. Numéro de notice : A2016-549 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2015-0027 En ligne : http://dx.doi.org/10.1515/jag-2015-0027 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81693
in Journal of applied geodesy > vol 10 n° 1 (March 2016) . - pp 5 - 16[article]Automatic geolocation correction of satellite imagery / Ozge C. Ozcanli in International journal of computer vision, vol 116 n° 3 (February 2016)
[article]
Titre : Automatic geolocation correction of satellite imagery Type de document : Article/Communication Auteurs : Ozge C. Ozcanli, Auteur ; Yi Dong, Auteur ; Joseph L. Mundy, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 263–277 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] alignement
[Termes IGN] coordonnées géodésiques
[Termes IGN] correction automatique
[Termes IGN] géolocalisation
[Termes IGN] géoréférencement
[Termes IGN] image satellite
[Termes IGN] modèle numérique de surface
[Termes IGN] OpenStreetMap
[Termes IGN] orthoimage
[Termes IGN] reconstruction 3D
[Termes IGN] réseau routierRésumé : (auteur) Modern satellites tag their images with geolocation information using GPS and star tracking systems. Depending on the quality of the geopositioning equipment, errors may range from a few meters to tens of meters on the ground. At the current state of art, there is no established method to automatically correct these errors limiting the large-scale joint utilization of cross-platform satellite images. In this paper, an automatic geolocation correction framework that corrects images from multiple satellites simultaneously is presented. As a result of the proposed correction process, all the images are effectively registered to the same absolute geodetic coordinate frame. The usability and the quality of the correction framework are demonstrated through a 3-D surface reconstruction application. The 3-D surface models given by original satellite geopositioning metadata, and the corrected metadata, are compared. The quality difference is measured through an entropy-based metric applied to the orthographic height maps given by the 3-D surface models. Measuring the absolute accuracy of the framework is harder due to lack of publicly available high-precision ground surveys. However, the geolocation of images of exemplar satellites from different parts of the globe are corrected, and the road networks given by OpenStreetMap are projected onto the images using original and corrected metadata to demonstrate the improved quality of alignment. Numéro de notice : A2016--146 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1007%2Fs11263-015-0852-7 En ligne : https://doi.org/10.1007/s11263-015-0852-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85905
in International journal of computer vision > vol 116 n° 3 (February 2016) . - pp 263–277[article]A multiscale masking method for point geographic data / K.C. Clarke in International journal of geographical information science IJGIS, vol 30 n° 1-2 (January - February 2016)
[article]
Titre : A multiscale masking method for point geographic data Type de document : Article/Communication Auteurs : K.C. Clarke, Auteur Année de publication : 2016 Article en page(s) : pp 300 - 315 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées
[Termes IGN] agrégation spatiale
[Termes IGN] C (langage)
[Termes IGN] droit privé
[Termes IGN] GeoTrans
[Termes IGN] Infrastructure de données
[Termes IGN] objet géographique ponctuel
[Termes IGN] protection de la vie privée
[Termes IGN] transformation de coordonnées
[Termes IGN] visualisation de donnéesRésumé : (auteur) This research introduces and tests a new masking technique for sensitive point-based geospatial data. The goal of masking is to allow data to be used for general measurements of spatial distributions, but to not permit the matching of points with their true underlying observations, usually street addresses, in order to protect identity and privacy. The proposed method first converts coordinates to the Military Grid Reference System (MGRS), then uses digit switching to mask coordinates. This permits encryption at five spatial levels of precision, equivalent to 1, 10, 100, 1000, and 10,000 m. Of the 1.3M possible digit switching combinations, one is chosen that minimizes the difference between the aggregate descriptive spatial statistics for the point set as a whole between the masked and the unmasked data. Most heavily weighted in the selection is the nearest neighbor statistic, a measure of clustering in the distribution. The masking method was implemented for point sets within a single MGRS cell square using NGA’s GEOTRANS software and new custom C language code, with both forward and inverse algorithms. The forward masking saves the translation code in a separate file without which the inversion is practically impossible, meaning that the masked data can be offered publicly. Four test point distributions were used to show the method in action. The method appears to offer new possibilities for the protection of sensitive geospatial data. Numéro de notice : A2016-089 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2015.1085540 En ligne : https://doi.org/10.1080/13658816.2015.1085540 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79874
in International journal of geographical information science IJGIS > vol 30 n° 1-2 (January - February 2016) . - pp 300 - 315[article]Réservation
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