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Improving dilution of precision: a companion measure of systematic effects / D. Milbert in GPS world, vol 20 n° 11 (November 2009)

Public [article]  inGPS world > vol 20 n° 11 (November 2009) . - pp 38 - 46 Titre : Improving dilution of precision: a companion measure of systematic effects Type de document : Article/Communication Auteurs : D. Milbert, Auteur Année de publication : 2009 Article en page(s) : pp 38 - 46 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] affaiblissement de la précision [Termes IGN] erreur aléatoire [Termes IGN] erreur de mesure [Termes IGN] erreur de positionnement [Termes IGN] erreur systématique [Termes IGN] mesurage de pseudo-distance [Termes IGN] modèle d'erreur [Termes IGN] positionnement par GNSS [Termes IGN] propagation d'erreur Résumé : (Editeur) [...] If we lived in an ideal world, a receiver could make perfect measurements and model them exactly. Then, we would only need measurements to any four satellites to determine our position perfectly. Unfortunately, the receiver must deal with measurements and models that have some degree of error, which gets propagated into the position solution. Furthermore, the geometrical arrangement of the satellites observed by the receiver their elevation angles and azimuths can significantly affect the precision and accuracy of the receiver's solution, typically degrading them. It is common to express the degradation or dilution by dilution of precision (DOP) factors. Multiplying the measurement and model uncertainty by an appropriate DOP value gives an estimate of the position error. These estimates are reasonable if the measurement and model errors are truly random. However, it turns out that this simple geometrical relationship breaks down if some model errors are systematic. If that systematic error is a constant bias and if it is common to all pseudoranges measured simultaneously, then the receiver can easily estimate it along with its clock offset, leaving the position solution unaffected. But if the errors are systematically different for the different simultaneous pseudoranges, as is typically the case when trying to correct for ionospheric and tropospheric effects, these errors propagate into the receiver solution in a way that is fundamentally different from the way that random errors propagate. This means that in addition to DOP, we need a companion measure of systematic effects. In this month's column, Dennis Milbert introduces just such a measure the error scale factor or ESF. ESF, combined with DOP, forms a hybrid error model that appears to more realistically portray the real-world GPS precisions and accuracies we actually experience. Copyright Questex Media Group Numéro de notice : A2009-407 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30038 [article]

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