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Auteur K. Wienholz
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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 descripteurs IGN] ambiguïté entière
[Termes descripteurs IGN] ligne de base
[Termes descripteurs IGN] logiciel de post-traitement GPS
[Termes descripteurs IGN] mesurage de phase
[Termes descripteurs IGN] modèle mathématique
[Termes descripteurs IGN] phase GPS
[Termes descripteurs IGN] propagation ionosphérique
[Termes descripteurs IGN] résolution d'ambiguïté
[Termes descripteurs IGN] traitement de données 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 :
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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