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Evaluation of NTCM-BC and a proposed modification for single-frequency positioning / Xiaohong Zhang in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1535 - 1548 Titre : Evaluation of NTCM-BC and a proposed modification for single-frequency positioning Type de document : Article/Communication Auteurs : Xiaohong Zhang, Auteur ; Fujian Ma, Auteur ; Xiaodong Ren, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 1535 - 1548 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] atténuation du signal [Termes IGN] modèle ionosphérique [Termes IGN] Neustrelitz TEC model NTCM [Termes IGN] positionnement par GNSS [Termes IGN] récepteur monofréquence [Termes IGN] teneur totale en électrons Résumé : (Auteur) Ionospheric delay is a dominant factor that affects the accuracy of single-frequency positioning. Thus, an empirical ionospheric model with high accuracy is very important for single-frequency users. This study proposes a modified empirical broadcast ionospheric model, called MNTCM-BC, based on the Neustrelitz Total Electron Content (TEC) broadcast model NTCM-BC. Nine daily ionospheric coefficients of these models are estimated using datasets of the previous day from 30 globally distributed Global Navigation Satellite System monitor stations, and the prediction performance of the MNTCM-BC is evaluated with the datasets of the current day from all 300 verification stations. The results show that the complex behavior of the ionosphere is well described by the MNTCM-BC, including the visibility of two ionization crests on both sides of the geomagnetic equator and the TEC variations that depend on the local time and geomagnetic latitude. In terms of the prediction accuracy, compared with the NTCM-BC, the main improvement in the MNTCM-BC is achieved in summer, whereas the accuracy is comparable in other seasons. Hence, the following analyses are focused on summer. In the low-solar activity year of 2009, the prediction accuracy of the MNTCM-BC is improved by 0.11 TECU compared with that of the NTCM-BC. As to the high-solar activity year of 2014, the corresponding improvement is 0.35 TECU. In addition, when the number of monitor stations is increased from 30 to 300, the prediction accuracy of two models can be slightly improved by 0.06 TECU in 2009 and 0.13 TECU in 2014, respectively, while reliability enhances. Furthermore, the average three-dimensional positioning accuracy of 160 globally distributed stations for single-frequency point positioning using the Klobuchar model, the NTCM-BC and the MNTCM-BC is 1.83, 1.21 and 1.20 m during quiet day and 3.15, 2.31 and 2.21 m during perturbed day, respectively. Relative to the Klobuchar model and the NTCM-BC, the average accuracy improvements in the MNTCM-BC are about 30 and 3%, respectively. Numéro de notice : A2017-615 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0631-8 En ligne : https://doi.org/10.1007/s10291-017-0631-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86925 [article]

Ionospheric correction using NTCM driven by GPS Klobuchar coefficients for GNSS applications / M.M. Hoque in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1563 - 1572 Titre : Ionospheric correction using NTCM driven by GPS Klobuchar coefficients for GNSS applications Type de document : Article/Communication Auteurs : M.M. Hoque, Auteur ; N. Jakowski, Auteur ; J. Berdermann, Auteur Année de publication : 2017 Article en page(s) : pp 1563 - 1572 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] atténuation du signal [Termes IGN] correction ionosphérique [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur monofréquence [Termes IGN] teneur totale en électrons Résumé : (Auteur) Global Navigation Satellite Systems (GNSS) require mitigation of ionospheric propagation errors because the ionospheric range errors might be larger than tens of meters at the zenith direction. Taking advantage of the frequency-dispersive property of ionospheric refractivity, the ionospheric range errors can be mitigated in dual-frequency applications to a great extent by a linear combination of carrier phases or pseudoranges. However, single-frequency GNSS operations require additional ionospheric information to apply signal delay or range error corrections. To aid single-frequency operations, the global positioning system (GPS) broadcasts 8 coefficients as part of the navigation message to drive the ionospheric correction algorithm (ICA) also known as Klobuchar model. We presented here an ionospheric correction algorithm called Neustrelitz TEC model (NTCM) which can be used as complementary to the GPS ICA. Our investigation shows that the NTCM can be driven by Klobuchar model parameters to achieve a significantly better performance than obtained by the mother ICA algorithm. Our research, using post-processed reference total electron content (TEC) data from more than one solar cycle, shows that on average the RMS modeled TEC errors are up to 40% less for the proposed NTCM model compared to the Klobuchar model during high solar activity period, and about 10% less during low solar activity period. Such an approach does not require major technology changes for GPS users rather requires only introducing the NTCM approach a complement to the existing ICA algorithm while maintaining the simplicity of ionospheric range error mitigation with an improved model performance. Numéro de notice : A2017-616 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0632-7 En ligne : https://doi.org/10.1007/s10291-017-0632-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86926 [article]

Computation of GPS P1–P2 differential code biases with JASON-2 / Gilles Wautelet in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1619 - 1631 Titre : Computation of GPS P1–P2 differential code biases with JASON-2 Type de document : Article/Communication Auteurs : Gilles Wautelet, Auteur ; Sylvain Loyer, Auteur ; Flavien Mercier, Auteur ; Félix Perosanz, Auteur Année de publication : 2017 Article en page(s) : pp 1619 - 1631 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] code GPS [Termes IGN] corrélation [Termes IGN] données Jason [Termes IGN] erreur systématique [Termes IGN] GPS en mode différentiel [Termes IGN] orbitographie [Termes IGN] plasmasphère [Termes IGN] teneur verticale totale en électrons Résumé : (Auteur) GPS Differential Code Biases (DCBs) computation is usually based on ground networks of permanent stations. The drawback of the classical methods is the need for the ionospheric delay so that any error in this quantity will map into the solution. Nowadays, many low-orbiting satellites are equipped with GPS receivers which are initially used for precise orbitography. Considering spacecrafts at an altitude above the ionosphere, the ionized contribution comes from the plasmasphere, which is less variable in time and space. Based on GPS data collected onboard JASON-2 spacecraft, we present a methodology which computes in the same adjustment the satellite and receiver DCBs in addition to the plasmaspheric vertical total electron content (VTEC) above the satellite, the average satellite bias being set to zero. Results show that GPS satellite DCB solutions are very close to those of the IGS analysis centers using ground measurements. However, the receiver DCB and VTEC are closely correlated, and their value remains sensitive to the choice of the plasmaspheric parametrization. Numéro de notice : A2017-617 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0638-1 Date de publication en ligne : 19/05/2017 En ligne : https://doi.org/10.1007/s10291-017-0638-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86927 [article]

Real-time multi-GNSS single-frequency precise point positioning / Peter F. de Bakker in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1791 - 1803 Titre : Real-time multi-GNSS single-frequency precise point positioning Type de document : Article/Communication Auteurs : Peter F. de Bakker, Auteur ; Christian C. J. M. Tiberius, Auteur Année de publication : 2017 Article en page(s) : pp 1791 - 1803 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur monofréquence [Termes IGN] temps réel [Termes IGN] test de performance Résumé : (Auteur) Precise Point Positioning (PPP) is a popular Global Positioning System (GPS) processing strategy, thanks to its high precision without requiring additional GPS infrastructure. Single-Frequency PPP (SF-PPP) takes this one step further by no longer relying on expensive dual-frequency GPS receivers, while maintaining a relatively high positioning accuracy. The use of GPS-only SF-PPP for lane identification and mapping on a motorway has previously been demonstrated successfully. However, the performance was shown to depend strongly on the number of available satellites, limiting the application of SF-PPP to relatively open areas. We investigate whether the applicability can be extended by moving from using only GPS to using multiple Global Navigation Satellite Systems (GNSS). Next to GPS, the Russian GLONASS system is at present the only fully functional GNSS and was selected for this reason. We introduce our approach to multi-GNSS SF-PPP and demonstrate its performance by means of several experiments. Results show that multi-GNSS SF-PPP indeed outperforms GPS-only SF-PPP in particular in case of reduced sky visibility. Numéro de notice : A2017-618 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0653-2 En ligne : https://doi.org/10.1007/s10291-017-0653-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86928 [article]

Assessment of PPP integer ambiguity resolution using GPS, GLONASS and BeiDou (IGSO, MEO) constellations / Yanyan Liu in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1647 – 1659 Titre : Assessment of PPP integer ambiguity resolution using GPS, GLONASS and BeiDou (IGSO, MEO) constellations Type de document : Article/Communication Auteurs : Yanyan Liu, Auteur ; Yidong Lou, Auteur ; Shirong Ye, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 1647 – 1659 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] ambiguïté entière [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GLONASS [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] qualité du signal [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) Global navigation satellite systems (GNSS) signal deformations could threaten the position accuracy and integrity of GNSS, especially for safety critical applications. Digital distortion is an important kind of deformations caused by failures inside the baseband generation unit onboard the GNSS satellites. Multi-correlator technique, as a prevalent signal quality monitoring (SQM) method, was developed to reliably detect the signal anomaly and therefore protect airborne users from this integrity threat. However, the conventional multi-correlator technique is unable to estimate the degree of distortion quantitatively, while another SQM method, the chip domain observable, has a poor real-time capability so that it could not meet the stringent time to alarm requirements. To solve the above problem, we derived the spectrum form of the conventional Threat Model A first and proposed a IFFT-based SQM algorithm. This new method can perform SQM easily by analyzing the impulses after PSD division and IFFT: Detect the presence of digital distortion by judging whether there is an impulse after IFFT and estimate the degree of distortion by computing the offset of the impulse. The results show that the IFFT-based method can not only detect digital distortion real-timely but also estimate the digital distortion degree quantitatively. Numéro de notice : A2017-619 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0641-6 En ligne : https://doi.org/10.1007/s10291-017-0641-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86929 [article]

GLONASS inter-frequency phase bias rate estimation by single-epoch or Kalman filter algorithm / Yi Bin Yao in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1871 – 1882 Titre : GLONASS inter-frequency phase bias rate estimation by single-epoch or Kalman filter algorithm Type de document : Article/Communication Auteurs : Yi Bin Yao, Auteur ; Mingxian Hu, Auteur ; Xiayan Xu, Auteur ; Yadong He, Auteur Année de publication : 2017 Article en page(s) : pp 1871 – 1882 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] double différence [Termes IGN] erreur de phase [Termes IGN] filtre de Kalman [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GLONASS [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) GLONASS double-differenced (DD) ambiguity resolution is hindered by the inter-frequency bias (IFB) in GLONASS observation. We propose a new algorithm for IFB rate estimation to solve this problem. Although the wavelength of the widelane observation is several times that of the L1 observation, their IFB errors are similar in units of meters. Based on this property, the new algorithm can restrict the IFB effect on widelane observation within 0.5 cycles, which means the GLONASS widelane DD ambiguity can be accurately fixed. With the widelane integer ambiguity and phase observation, the IFB rate can be estimated using single-epoch measurements, called the single-epoch IFB rate estimation algorithm, or using the Kalman filter to process all data, called the Kalman filter-based IFB rate estimation algorithm. Due to insufficient accuracy of the IFB rate estimated from widelane observations, the IFB rate has to be further refined with L1 and L2 observations. A new reference satellite selection method is proposed to serve the IFB rate estimation. The experiment results show that the IFB rates on L1 and L2 bands are different, that an accurate IFB rate will help us to obtain more fixed solutions at places with serious occlusion, that the single-epoch IFB rate estimation algorithm can meet the requirements for real-time kinematic positioning with only 8% extra computational time, and that the Kalman filter-based IFB rate estimation algorithm is a satisfactory option for high-accuracy GLONASS positioning. Numéro de notice : A2017-620 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0660-3 En ligne : https://doi.org/10.1007/s10291-017-0660-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86930 [article]

3D building model-assisted snapshot positioning algorithm / Rakesh Kumar in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1923 - 1935 Titre : 3D building model-assisted snapshot positioning algorithm Type de document : Article/Communication Auteurs : Rakesh Kumar, Auteur ; Mark G. Petovello, Auteur Année de publication : 2017 Article en page(s) : pp 1923 - 1935 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] Calgary [Termes IGN] compensation par moindres carrés [Termes IGN] corrélateur [Termes IGN] lancer de rayons [Termes IGN] milieu urbain [Termes IGN] modèle 3D de l'espace urbain [Termes IGN] positionnement par GNSS [Termes IGN] récepteur GNSS [Termes IGN] résidu [Termes IGN] trajet multiple Résumé : (Auteur) A method for constructively using non-line-of-sight GNSS signals from a snapshot of signal samples for positioning of users in urban areas is presented here. Using a 3D building model and a ray-tracing algorithm, the number of reception paths and the corresponding path delays of reflected signals are predicted, across a rid of candidate positions. These predictions are then used to compute a least squares fit to the GNSS receiver’s correlator outputs, and the position with smallest residuals is selected as the position estimate. Using data collected along 3.5 km of road in downtown Calgary, Canada, where buildings reach heights of over 200 m, the root-mean-square position error is below 10 m in the along-track and across-track directions. Compared to two pseudorange-based receivers, the proposed method yields RMS error improvements of at least 31% in the along-track direction, 63% in the across-track direction, and 53% in the horizontal plane. Numéro de notice : A2017-621 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0661-2 En ligne : https://doi.org/10.1007/s10291-017-0661-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86931 [article]