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Accuracy versus precision: a primer on GPS truth / D. Rutledge in GPS world, vol 21 n° 5 (May 2010)

Public [article]  inGPS world > vol 21 n° 5 (May 2010) . - pp 42 - 49 Titre : Accuracy versus precision: a primer on GPS truth Type de document : Article/Communication Auteurs : D. Rutledge, Auteur Année de publication : 2010 Article en page(s) : pp 42 - 49 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction du signal [Termes IGN] distribution de Gauss [Termes IGN] erreur aléatoire [Termes IGN] erreur systématique [Termes IGN] précision du positionnement [Termes IGN] signal GPS Résumé : (Editeur) All measurements contain errors. To extract the most useful amount of information from the measurements, the errors must be properly analyzed. Errors can be broadly grouped into two major categories: biases, which are systematic and which can be modeled in an equation describing the measurements, thereby removing or significantly reducing their effect; and noise or random error, each value of which cannot be modeled but whose statistical properties can be used to optimize the analysis results. Take GPS carrier-phase measurements, for example. It is a standard approach to collect measurements at a reference station and a target station and to form the double differences of the measurements between pairs of satellites and the pair of receivers. By so doing, the biases in the modeled measurements that are common to both receivers, such as residual satellite clock error, are canceled or significantly reduced. However, the random error in the measurements due to receiver thermal noise and the quasi-random effect of multipath cannot be differenced away. If we estimate the coordinates of the target receiver at each epoch of the measurements, how far will they be from the true coordinates? That depends on how well the biases were removed and the effects of random error. By comparing the results from many epochs of data, we might see that the coordinate values agree amongst themselves quite closely; they have high precision. But, due to some remaining bias, they are offset from the true value; their accuracy is low. Two different but complementary measures for assessing the quality of the results. In this month's column, we will examine the differences between the precision and accuracy of GPS-determined positions and, armed with a better understanding of these often confused terms, perhaps be less likely to abuse the truth in the business of GPS positioning. Copyright Questex Media Group Numéro de notice : A2010-166 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30361 [article]

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Dam stability: assessing the performance of a GPS monitoring system / D. Rutledge in GPS world, vol 17 n° 10 (October 2006)

Public [article]  inGPS world > vol 17 n° 10 (October 2006) . - pp 26 - 33 Titre : Dam stability: assessing the performance of a GPS monitoring system Type de document : Article/Communication Auteurs : D. Rutledge, Auteur ; S.Z. Meyerholtz, Auteur ; N. Brown, Auteur ; C.S. Baldwin, Auteur Année de publication : 2006 Article en page(s) : pp 26 - 33 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] auscultation d'ouvrage [Termes IGN] barrage [Termes IGN] centrale hydroélectrique [Termes IGN] Montana (Etats-Unis) [Termes IGN] positionnement par GPS [Termes IGN] surveillance d'ouvrage [Termes IGN] topométrie de précision Résumé : (Auteur) A precise and modernized monitoring program is an important component of the US Army Corps of Engineers' long-term risk-management plan for hydroelectric structures. Recent work at Libby Dam in Montana demonstrates that GPS deformation monitoring systems can accurately track displacements at critical points, making it an important asset in ensuring dam safety. Copyright Questex Media Group Inc Numéro de notice : A2006-446 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28170 [article]

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Staying afloat: GPS monitors oilfield subsidence / D. Rutledge in GPS world, vol 13 n° 10 (October 2002)

Public [article]  inGPS world > vol 13 n° 10 (October 2002) . - pp 12 - 18 Titre : Staying afloat: GPS monitors oilfield subsidence Type de document : Article/Communication Auteurs : D. Rutledge, Auteur ; et al., Auteur Année de publication : 2002 Article en page(s) : pp 12 - 18 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Californie (Etats-Unis) [Termes IGN] déformation de la croute terrestre [Termes IGN] GPS en mode pseudo-cinématique [Termes IGN] nivellement par GPS [Termes IGN] pétrole [Termes IGN] positionnement par GPS [Termes IGN] station permanente [Termes IGN] subsidence [Termes IGN] surveillance géologique Résumé : (Auteur) The City of Long Beach, california, is currently replacing traditional spirit leveling techniques with fixed and mobile GPS methods to gather precise information about subsidence and rebound associated with the Wilmington Oil Field. This shift has reduced the data collection time and begun to provide timelier information that engineers can use to better mitigate any deformation effects. Numéro de notice : A2002-393 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26417 [article]

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