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Analysis of the design parameters of multi-reference station RTK GPS networks / Ahmed El-Mowafy in Surveying and land information science, vol 65 n° 1 (01/03/2005)
[article]
Titre : Analysis of the design parameters of multi-reference station RTK GPS networks Type de document : Article/Communication Auteurs : Ahmed El-Mowafy, Auteur Année de publication : 2005 Article en page(s) : pp 17 - 26 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] Doubaï
[Termes IGN] GPS en mode cinématique
[Termes IGN] ligne de base
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] réseau géodésique local
[Termes IGN] station de référence
[Termes IGN] station GPS
[Termes IGN] station virtuelle
[Termes IGN] tachéomètre électronique
[Termes IGN] temps réelRésumé : (Auteur) In this study, the main design parameters of multi-reference station RTK-GPS networks have been analyzed, and their impact on the achieved positioning performance and phase ambiguity resolution is discussed. The main parameters considered are: the distance separating reference stations, network configuration, communication between the computing center and the user, and network algorithm. A number of tests have been conducted in a case study utilizing the Dubai Virtual Reference Network System (DVRS) in the United Arab Emirates. First, the real-time performance of the existing network was assessed. Next, the performance of the network was evaluated in a post-mission processing after making changes to its design, addressing the above parameters, by adding data from three auxiliary reference stations. Different network configurations were examined, consisting of variable combinations of the DVRS and the auxiliary stations. In addition, positioning results of two network algorithms (FKP/VRS and the Multiref methods) were compared. Finally, recommendations concerning the selection of baseline lengths, network architecture and station redundancy have been given. Numéro de notice : A2005-281 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27417
in Surveying and land information science > vol 65 n° 1 (01/03/2005) . - pp 17 - 26[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 121-05011 RAB Revue Centre de documentation En réserve L003 Disponible Ordering points for incremental TIN construction from DEMs / J.J. Little in Geoinformatica, vol 7 n° 1 (March - May 2003)
[article]
Titre : Ordering points for incremental TIN construction from DEMs Type de document : Article/Communication Auteurs : J.J. Little, Auteur ; P. Shi, Auteur Année de publication : 2003 Article en page(s) : pp 33 - 53 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie numérique
[Termes IGN] erreur absolue
[Termes IGN] erreur aléatoire
[Termes IGN] erreur moyenne quadratique
[Termes IGN] ligne de base
[Termes IGN] modèle numérique de terrain
[Termes IGN] Triangulated Irregular NetworkRésumé : (Auteur) The standard method of building compact triangulated surface approximations to terrain surfaces (TINs) from dense digital elevation models (DEMs) adds points to an initial sparse triangulation or removes points from a dense initial mesh. Typically, in each triangle in the current TIN, the worst fitting point, in terms of vertical distance, is selected. The order of insertion of the points is determined by the magnitude of the maximum vertical difference. This measure produces triangulations that minimize the maximum vertical distance between the TIN and the source DEM. Other approximation criteria are often used, however, including the rootmeansquared error or the mean absolute error, both for the vertical difference and normal difference, i.e., the distance in the direction of the normal to the triangular approximation. For these approximation criteria, we still select the worst fit point, but determine the insertion order by various sums of' errors over the triangle. Experiments show that using these better evaluation measures significantly reduces the size of the TIN for a given approximation error. Numéro de notice : A2003-060 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1023/A:1022870110853 En ligne : https://doi.org/10.1023/A:1022870110853 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22356
in Geoinformatica > vol 7 n° 1 (March - May 2003) . - pp 33 - 53[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 057-03011 RAB Revue Centre de documentation En réserve L003 Disponible Zur Bestimmung der GPS-Phasenmehrdeutigkeiten in großräumigen Netzen / K. Wienholz (2003)
Titre : Zur Bestimmung der GPS-Phasenmehrdeutigkeiten in großräumigen Netzen Titre original : [Vers la résolution des ambiguïtés de phase GPS dans les réseaux à grande échelle] Type de document : Thèse/HDR Auteurs : K. Wienholz, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2003 Collection : DGK - C Sous-collection : Dissertationen num. 566 Importance : 102 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5005-1 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] ambiguïté entière
[Termes IGN] ligne de base
[Termes IGN] logiciel de post-traitement GPS
[Termes IGN] mesurage de phase
[Termes IGN] modèle mathématique
[Termes IGN] phase GPS
[Termes IGN] propagation ionosphérique
[Termes IGN] résolution d'ambiguïté
[Termes IGN] traitement de données GNSSIndex. décimale : 30.61 Systèmes de Positionnement par Satellites du GNSS Résumé : (Auteur) The development and the results of the TUB method are presented in this paper. This special method serves in resolving GPS phase ambiguities in small-range and large-range networks. It is characterized by taking into account the correlates as quality criteria, thus enabling an assessment of the calculated ambiguities. First of all : by simulating an example to mediate the adjustment of conditions between unknown quantities it can be shown that every incorrect condition exerts a major constraint on the adjustment system. This constraint is reflected by the pertaining Lagrange factors (or correlates), the value of which increases rapidly in line with the magnitude of error in the equation of condition. This knowledge can be used in the TUB method to investigate various parameters. However, in this paper the emphasis is on the investigation of ambiguities.
The TUB method is based on a special parameterization of the observation equations so that several unknown parameters are combined in one newly established time-dependent auxiliary parameter and in one timeindependent auxiliary parameter. By reduction of the unknown parameters a stable equation system is brought about which can be solved without resulting in differences and linear combinations. The direct analysis of original phase observations prevents the error-propagation of accidental errors and hence an artificial increase in phase noise. Therefore the confidence intervals, characterized by integer numbers, can be kept rather small. In finding these integer numbers the time-dependent auxiliary parameters must first be separated in different ways, depending on the lengths of the base lines, from the ionospheric refraction. Then the ambiguities in the form of double differences, related to a base satellite and a base station (or in the form of L1/L2 ambiguity pairs), can be solved in an iterative process. As a controlling device equations of condition are formed with the help of L1/L2 ambiguity pairs and inserted in the adjustment process. A subsequent analysis of the correlates gives information about the qualities of the ambiguities found.
To begin with the potential of the TUB method is tested by means of a data set with base line lengths ranging from 13 to 48 km. By analyzing the correlates incorrect double difference ambiguities can be identified and among several integer numbers the correct one is filtered out. In two further nets with base line lengths from 26 to 106 km the influences of various more or less accurate orbits on the parameters of the observation equations are investigated. In the aforementioned examples a resolution of the ambiguities is possible at a success rate of 100 percent while an observation time of about two hours is sufficient. When terrain points are between 700 and 1000 km apart the model shows consider-able inaccuracies. The evaluation of data stemming from various IGS stations evidences that in about 20 percent of all ambiguities integer numbers cannot be found. In these cases the confidence intervals either do not provide any integer number or too many of them. In the latter case there are, instead of a single one, several LI/L2 ambiguity pairs that do not differ very much from one another. When these ambiguity pairs are inserted in the equation system the values of the correlates do not differ very much either. For the time being no satisfactory results can be achieved for base lines ranging between 1000 and 2000 km.
The analysis of the correlates proves to be a useful tool in evaluating the quality of ambiguities. The correlates with the highest values occur when incorrect ambiguities exert major constraints on the equations of condition. In these cases errors can be detected, e.g., those arising from the use of broad-cast ephemerides. When several integer numbers are found in the confidence intervals the values of the correlates suggest values matching the normal equation system. Considerable interdependencies of the equations of condition are evident. Consequently there is an increase in the values that are linked to an incorrect condition via satellite and station. Therefore the correlations between the Lagrange factors should be investigated more closely. It is useful to determine the ambiguities of a data set by observation times of different lengths. By comparing the double difference ambiguities calculated from these solutions an additional examination of the results is made possible. Particularly when base lines of more than 1000 km are used it turns out that with data resulting from shorter observation times integer numbers can be calculated that would either not result at all or only inaccurately from longer measurements. The use of correlates as indicators for incorrect conditions is not only suitable for evaluating ambiguities in GPS analysis. Moreover, all parameters that can be formulated in appropriate conditions may be examined in any case of problems regarding the analysis of data.Numéro de notice : 13191 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54906 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 13191-02 30.61 Livre Centre de documentation Géodésie Disponible 13191-01 30.61 Livre Centre de documentation Géodésie Disponible Scale and orientation-invariant scene similarity metrics for image queries / A. Stefanidis in International journal of geographical information science IJGIS, vol 16 n° 8 (december 2002)
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Titre : Scale and orientation-invariant scene similarity metrics for image queries Type de document : Article/Communication Auteurs : A. Stefanidis, Auteur ; Peggy Agouris, Auteur ; C. Georgiadis, Auteur ; Michela Bertolotto, Auteur ; James D. Carswell, Auteur Année de publication : 2002 Article en page(s) : pp 749 - 772 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] analyse numérique
[Termes IGN] ligne de base
[Termes IGN] photo-interprétation assistée par ordinateur
[Termes IGN] rectangle englobant minimum
[Termes IGN] relation topologique
[Termes IGN] requête (informatique)
[Termes IGN] similitude
[Termes IGN] variation d'échelleRésumé : (Auteur) In this paper, we extend our previous work on shapebased queries to support queries on configurations of image objects. Here we consider spatial reasoning, especially directional and metric object relationships. Existing models for spatial reasoning tend to rely on pre-identified cardinal directions and minimal scale variations, assumptions that cannot be considered as given in our image applications, where orientations and scale may vary substantially, and are often unknown. Accordingly, we have developed the method of varying baselines to identify similarities in direction and distance relations. Our method allows us to evaluate directional similarities without a priori knowledge of cardinal directions, and to compare distance relations even when query scene and database content differ in scale by unknown amounts. We use our method to evaluate similarity between a userdefined query scene and object configurations. Here we present this new method, and discuss its role within a broader image retrieval framework. Numéro de notice : A2002-258 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/13658810210148552 En ligne : https://doi.org/10.1080/13658810210148552 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22169
in International journal of geographical information science IJGIS > vol 16 n° 8 (december 2002) . - pp 749 - 772[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 079-02081 RAB Revue Centre de documentation En réserve L003 Disponible The effect of broadleaf canopies on survey-grade horizontal GPS-GLONASS measurements / Thomas H. Meyer in Surveying and land information systems, vol 62 n° 4 (01/12/2002)
[article]
Titre : The effect of broadleaf canopies on survey-grade horizontal GPS-GLONASS measurements Type de document : Article/Communication Auteurs : Thomas H. Meyer, Auteur ; J.E. Bean, Auteur ; C.R. Ferguson, Auteur ; J.M. Naismith, Auteur Année de publication : 2002 Article en page(s) : pp 215 - 224 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] diffusion du rayonnement
[Termes IGN] feuille (végétation)
[Termes IGN] instrumentation Trimble
[Termes IGN] ligne de base
[Termes IGN] positionnement par GLONASS
[Termes IGN] positionnement par GPS
[Termes IGN] récepteur GPS
[Termes IGN] récepteur mixte
[Termes IGN] seuillage
[Termes IGN] signal GLONASS
[Termes IGN] signal GPSRésumé : (Auteur) A study was conducted to empirically determine the degradation of survey-grade GPS horizontal position measurements due to the effects of broadleaf forest canopies. The measurements were taken using GPS/GLONASS-capable receivers measuring C/A and P-codes, and carrier phase. Fourteen survey markers were chosen in central Connecticut to serve as reference makers for study. These markers had varying degrees of sky obstruction due to overhanging tree canopies. Sky obstruction was measured by photographing the sky with a 35 mm reflex camera fitted with a hemispherical lens. The negative was scanned and the image mapped using an equal-area projection to remove the distortion caused by the lens. The resulting digital image was thresholded to produce a black-and-white image in which a count of the black pixels is a measure of sky-area obstruction. The locations of the markers were determined independently before the study. During the study, each marker was occupied for four 20-minutes sessions over the period of one week in mid-july 1999. The locations of the study markers produced relatively long baselines, as compared with similar studies. We compared the accuracy of GPS-only vs. GPS&GLONASS as a function of sky obstruction. Based on our results, GLONASS observations did not improve of degrade the accuracy of the position measurements. There is a loss of 2 mm of accuracy per percent of sky obstruction for both GPS only and GPS&GLONASS. Numéro de notice : A2002-360 Affiliation des auteurs : non IGN Thématique : FORET/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22271
in Surveying and land information systems > vol 62 n° 4 (01/12/2002) . - pp 215 - 224[article]Topographic SAR interferometry formulation for high-précision DEM generation / R. Abdelfattah in IEEE Transactions on geoscience and remote sensing, vol 40 n° 11 (November 2002)PermalinkMulti-baseline polarimetric SAR interferometry-first experimental spaceborne and airborne results / O. Stebler in ISPRS Journal of photogrammetry and remote sensing, vol 56 n° 3 (April - June 2002)PermalinkFirst precise results of VLBI observation of the baseline in Antarctic plate / Yoshihiro Fukuzaki in Bulletin of the Geographical survey institute, vol 48 (March 2002)PermalinkThe Geodetic Antarctic Project GAP95. German contributions to the SCAR 95 Epoch campaign / R. Dietrich (1996)PermalinkAtmospheric pressure loading effects on global positioning system coordinate determinations / Tonie M. VanDam in Journal of geophysical research : Solid Earth, vol 99 n° 12 (10/12/1994)PermalinkA parametrized solid Earth tide model and ocean tide loading effects for global geodetic baseline measurements / H. Scherneck in Geophysical journal international, vol 106 n° 3 (September 1991)PermalinkContributions to GPS studies / Chris Rizos (1990)PermalinkGinfest, GPS proposals comparison of medium and long baselines determined by GPS, SLR, and VLBI / H. Seeger (01/12/1985)PermalinkThe interstation distance Metsahovi - Potsdam based on satellite measurements / H. Montag (1984)PermalinkDétermination des lignes de base par interférométrie radio / Claude Boucher (03/02/1981)Permalink