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Indoor positioning using differential Wi-Fi lateration / Guenther Retscher in Journal of applied geodesy, vol 11 n° 4 (December 2017)  

Public [article]  inJournal of applied geodesy > vol 11 n° 4 (December 2017) . - pp 249 - 269 Titre : Indoor positioning using differential Wi-Fi lateration Type de document : Article/Communication Auteurs : Guenther Retscher, Auteur ; Thomas Tatschl, Auteur Année de publication : 2017 Article en page(s) : pp 249 - 269 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes descripteurs IGN] appareil portable [Termes descripteurs IGN] multilatération [Termes descripteurs IGN] positionnement en intérieur [Termes descripteurs IGN] positionnement par WiFi Résumé : (Auteur) For Wi-Fi positioning usually location fingerprinting or (tri)lateration are employed whereby the received signal strengths (RSSs) of the surrounding Wi-Fi Access Points (APs) are scanned on the mobile devices and used to perform localization. Within the scope of this study, the position of a mobile user is determined on the basis of lateration. Two new differential approaches are developed and compared to two common models, i.e., the one-slope and multi-wall model, for the conversion of the measured RSS of the Wi-Fi signals into ranges. The two novel methods are termed DWi-Fi as they are derived either from the well-known DGPS or VLBI positioning principles. They make use of a network of reference stations deployed in the area of interest. From continuous RSS observations on these reference stations correction parameters are derived and applied by the user in real-time. This approach leads to a reduced influence of temporal and spatial variations and various propagation effects on the positioning result. In practical use cases conducted in a multi-storey office building with three different smartphones, it is proven that the two DWi-Fi approaches outperform the common models as static positioning yielded to position errors of about 5 m in average under good spatial conditions. Numéro de notice : A2017-791 Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2017-0011 En ligne : https://doi.org/10.1515/jag-2017-0011 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89063 [article]

Congruence analysis of geodetic networks, hypothesis tests versus model selection by information criteria / Rüdiger Lehmann in Journal of applied geodesy, vol 11 n° 4 (December 2017)  

Public [article]  inJournal of applied geodesy > vol 11 n° 4 (December 2017) . - pp 271 - 283 Titre : Congruence analysis of geodetic networks, hypothesis tests versus model selection by information criteria Type de document : Article/Communication Auteurs : Rüdiger Lehmann, Auteur ; Michael Lösler, Auteur Année de publication : 2017 Article en page(s) : pp 271 - 283 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes descripteurs IGN] analyse de données [Termes descripteurs IGN] congruence [Termes descripteurs IGN] déformation géométrique [Termes descripteurs IGN] réseau géodésique Résumé : (Auteur) Geodetic deformation analysis can be interpreted as a model selection problem. The null model indicates that no deformation has occurred. It is opposed to a number of alternative models, which stipulate different deformation patterns. A common way to select the right model is the usage of a statistical hypothesis test. However, since we have to test a series of deformation patterns, this must be a multiple test. As an alternative solution for the test problem, we propose the p-value approach. Another approach arises from information theory. Here, the Akaike information criterion (AIC) or some alternative is used to select an appropriate model for a given set of observations. Both approaches are discussed and applied to two test scenarios: A synthetic levelling network and the Delft test data set. It is demonstrated that they work but behave differently, sometimes even producing different results. Hypothesis tests are well-established in geodesy, but may suffer from an unfavourable choice of the decision error rates. The multiple test also suffers from statistical dependencies between the test statistics, which are neglected. Both problems are overcome by applying information criterions like AIC. Numéro de notice : A2017-792 Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2016-0049 En ligne : https://doi.org/10.1515/jag-2016-0049 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89064 [article]