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PPP-RTK: from common-view to all-in-view GNSS networks / Baocheng Zhang in Journal of geodesy, vol 96 n° 12 (December 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 12 (December 2022) . - n° 102 Titre : PPP-RTK: from common-view to all-in-view GNSS networks Type de document : Article/Communication Auteurs : Baocheng Zhang, Auteur ; Pengyu Hou, Auteur ; Robert Odolinski, Auteur Année de publication : 2022 Article en page(s) : n° 102 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] erreur de phase [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] résolution d'ambiguïté Résumé : (auteur) Integer ambiguity resolution-enabled precise point positioning (PPP), otherwise known as PPP real-time kinematic (PPP-RTK), recovers the integer nature of ambiguities at a user receiver by delivering the satellite phase biases (SPBs) estimated from a global navigation satellite system (GNSS) network. Due to the rank-deficiency existing between the satellite and receiver phase biases and the ambiguities, the formulation of PPP-RTK model needs to choose a set of unknown parameters as the datum (or the S-basis). Despite the fact that there are non-unique datum choices, one prefers a PPP-RTK model where the estimable SPBs contain a minimum number of datum ambiguities. We will show that otherwise there will be discontinuities occurring in datum ambiguities that will lead to unfavorable jumps in the estimated SPBs and frequent ambiguity resolution (re-)initialization on the user side. For this to occur one normally restricts to a common-view (CV) network, where the satellites are commonly visible to all receivers involved, and constructs the PPP-RTK model by choosing the phase biases and the ambiguities, pertaining to one receiver, as the datum. In doing so the CV model is capable of estimating the SPBs with each bias containing only one datum ambiguity. In this contribution we extend the CV model to an all-in-view (AV) network case where the satellites tracked can differ across receivers, but at least one satellite is commonly visible; this is practical as the network size is normally consisting of baseline lengths of several hundreds of kilometers. Contrary to the CV model, in the AV model the phase biases and the ambiguities pertaining to one satellite is selected as the datum, such that, the number of datum ambiguities entering into the estimable SPBs is always at the minimum as the SPBs are formulated in a between-satellite single-differenced form. The benefits with AV model are that it relieves the stringent satellite visibility as required by the CV model and, at the same time, reduces to the best possible extent any jumps in the estimated SPBs as well as the necessary ambiguity resolution (re-)initialization on the user side. Experiments conducted using multi-GNSS data collected in both CV and AV networks verify that the AV model always outperforms the CV one, as measured by both the time-to-first-fix as well as the positioning accuracy when compared to very precise benchmark coordinates. Numéro de notice : A2022-899 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01693-y Date de publication en ligne : 13/12/2022 En ligne : https://doi.org/10.1007/s00190-022-01693-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102257 [article]

GCPs-free photogrammetry for estimating tree height and crown diameter in Arizona cypress plantation using UAV-mounted GNSS RTK / Morteza Pourreza in Forests, vol 13 n° 11 (November 2022)  

Public [article]  inForests > vol 13 n° 11 (November 2022) . - n° 1905 Titre : GCPs-free photogrammetry for estimating tree height and crown diameter in Arizona cypress plantation using UAV-mounted GNSS RTK Type de document : Article/Communication Auteurs : Morteza Pourreza, Auteur ; Fardin Moradi, Auteur ; Mohammad Khosravi, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 1905 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] cupressus (genre) [Termes IGN] diamètre des arbres [Termes IGN] hauteur de vol [Termes IGN] hauteur des arbres [Termes IGN] image captée par drone [Termes IGN] Iran [Termes IGN] modèle numérique de surface de la canopée [Termes IGN] point d'appui [Termes IGN] positionnement cinématique en temps réel [Termes IGN] structure-from-motion Résumé : (auteur) One of the main challenges of using unmanned aerial vehicles (UAVs) in forest data acquisition is the implementation of Ground Control Points (GCPs) as a mandatory step, which is sometimes impossible for inaccessible areas or within canopy closures. This study aimed to test the accuracy of a UAV-mounted GNSS RTK (real-time kinematic) system for calculating tree height and crown height without any GCPs. The study was conducted on a Cupressus arizonica (Greene., Arizona cypress) plantation on the Razi University Campus in Kermanshah, Iran. Arizona cypress is commonly planted as an ornamental tree. As it can tolerate harsh conditions, this species is highly appropriate for afforestation and reforestation projects. A total of 107 trees were subjected to field-measured dendrometric measurements (height and crown diameter). UAV data acquisition was performed at three altitudes of 25, 50, and 100 m using a local network RTK system (NRTK). The crown height model (CHM), derived from a digital surface model (DSM), was used to estimate tree height, and an inverse watershed segmentation (IWS) algorithm was used to estimate crown diameter. The results indicated that the means of tree height obtained from field measurements and UAV estimation were not significantly different, except for the mean values calculated at 100 m flight altitude. Additionally, the means of crown diameter reported from field measurements and UAV estimation at all flight altitudes were not statistically different. Root mean square error (RMSE Numéro de notice : A2022-838 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.3390/f13111905 Date de publication en ligne : 12/11/2022 En ligne : https://doi.org/10.3390/f13111905 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102039 [article]

A new partial ambiguity resolution method based on modified solution separation and GNSS epoch-differencing / Yang Jiang in Journal of geodesy, vol 96 n° 11 (November 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 11 (November 2022) . - n° 88 Titre : A new partial ambiguity resolution method based on modified solution separation and GNSS epoch-differencing Type de document : Article/Communication Auteurs : Yang Jiang, Auteur ; Wei Ding, Auteur ; Yuting Gao, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 88 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] compensation Lambda [Termes IGN] erreur de positionnement [Termes IGN] phase [Termes IGN] positionnement cinématique en temps réel [Termes IGN] récepteur GNSS [Termes IGN] résolution d'ambiguïté Résumé : (auteur) Partial ambiguity resolution has been widely used in real-time kinematic (RTK) positioning to provide accurate and continuous centimeter-level positioning solutions. Current PAR methods are concerned with the exclusion of ambiguities that otherwise would result in low rate of full ambiguity resolution (FAR). With an assumption of unbiased ambiguities, the traditional PAR methods use the ambiguity-domain test statistics and probability-domain quantitative evaluation to select and validate the ambiguity subset. Consequentially, they would degrade the performance using low-cost devices in challenging environments where ambiguity biases exist, causing high probabilities of false alarm and missed detection of PAR and subsequently poor availability and accuracy of PAR. To deal with this issue, in this study, we propose a new PAR method for application in challenging environments. The proposed method consists of two major steps. First, a global navigation satellite system epoch-differencing (GED) algorithm is applied to derive a prior ambiguity solution. Second, we use a modified solution separation (SS) method with the prior ambiguity solution as an external input to obtain more accurate ambiguity test statistics. Based on a dynamic road test under environments with significant signal blockages, the performance of the proposed method is analyzed by using a low-cost GNSS receiver. The proposed method provides ambiguity test statistics with higher accuracy and can achieve 73.19% and 50.55% improvement in the accuracy and availability of the fixed solution, compared with the traditional PAR methods. Besides, the RMS of positioning errors with fixed solution are 1.03 cm, 0.70 cm, and 1.50 cm for the proposed PAR method in the east, north, and upward directions, respectively, which are 1.06 cm, 0.72 cm, and 1.35 cm for SS-based PAR, and 5.29 cm, 0.86 cm, and 5.56 cm for ILS-based PAR. The proposed PAR method achieves 90.36% fixed epochs, versus 79.06%, and 88.28%, for ILS-based PAR and SS-based PAR, respectively. Numéro de notice : A2022-810 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01674-1 Date de publication en ligne : 02/11/2022 En ligne : https://doi.org/10.1007/s00190-022-01674-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101967 [article]

PPP–RTK theory for varying transmitter frequencies with satellite and terrestrial positioning applications / Peter J.G. Teunissen in Journal of geodesy, vol 96 n° 11 (November 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 11 (November 2022) . - n° 84 Titre : PPP–RTK theory for varying transmitter frequencies with satellite and terrestrial positioning applications Type de document : Article/Communication Auteurs : Peter J.G. Teunissen, Auteur ; Amir Khodabandeh, Auteur Année de publication : 2022 Article en page(s) : n° 84 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] ambiguïté entière [Termes IGN] fréquence [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] théorie de l'estimation Résumé : (auteur) In this contribution, we generalize PPP–RTK theory by allowing the transmitters to transmit on different frequencies. The generalization is based on the integer-estimability theory of Teunissen (A new GLONASS FDMA model. GPS Solutions, 2019). As the theory and associated algorithms provided are generally applicable, they apply to satellite-based carrier-phase positioning as well as to terrestrial interferometric sensory networks. Based on an identification of the constraints imposed on the admissible ambiguity transformations by PPP–RTK, a fundamental network+user condition is found that determines whether PPP–RTK is possible or not. The discriminating contributions of both the network and user observation equations to this PPP–RTK condition are analysed, followed by a description of PPP–RTK enabling classes of measurement scenarios. Numéro de notice : A2022-796 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s00190-022-01665-2 Date de publication en ligne : 26/10/2022 En ligne : https://doi.org/10.1007/s00190-022-01665-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101934 [article]

An efficient method to compensate receiver clock jumps in real-time precise point positioning / Shaoguang Xu in Remote sensing, vol 14 n° 20 (October-2 2022)  

Public [article]  inRemote sensing > vol 14 n° 20 (October-2 2022) . - n° 5222 Titre : An efficient method to compensate receiver clock jumps in real-time precise point positioning Type de document : Article/Communication Auteurs : Shaoguang Xu, Auteur ; Jialu Long, Auteur ; Jinling Wang, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 5222 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] décalage d'horloge [Termes IGN] erreur de positionnement [Termes IGN] glissement de cycle [Termes IGN] horloge du récepteur [Termes IGN] phase [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] retard troposphérique zénithal [Termes IGN] temps réel Résumé : (auteur) In global navigation satellite systems (GNSSs)-based positioning, user receiver clock jump is a common phenomenon on the low-cost receiver clocks and can break the continuity of observation time tag, carrier phase and pseudo range. The discontinuity may affect precise point positioning-related parameter estimation, including receiver clock error, position, troposphere and ionosphere parameters. It is important to note that these parameters can be used for timing, positioning, atmospheric inversion and so on. In response to this problem, the receiver clock jumps are divided into two types. The first one can be expressed by the carrier phase and pseudo range having the same scale jump, and the second one is that they are having different scale jumps. For the first type, if a small priori variance of receiver clock error is provided, it can affect the accuracy of ionospheric delay estimation both in static and kinematic mode, while in the latter mode, it also affects position estimation. However, if large process noise is provided, numerical problems may arise since other parameters’ process noises are usually small, it is proposed to use the single point positioning with pseudo ranges to provide a priori value of receiver clock error, and an empiric value is assigned to its prior variance, this handle can avoid the above problems. For the second type, instead of compensating so many raw observations in the traditional methods, it is proposed to compensate the ambiguities at the clock jump epochs only in a new method. The new method corrects the Melbourne–Wubbena (MW) combination firstly in order to avoid the misjudging of cycle slips for current epoch, and the second step is to compensate the corresponding ambiguities, then, after Kalman filtering, the MW and its mean should be corrected back in order to avoid the misjudging of cycle slips at the next epoch. This approach has the advantage of handling the clock jump epoch-wise and can avoid correcting the rest of the observations as the traditional methods used to. With the numerical validation examples both in static and kinematic modes, it shows the new method is simple but efficient for real time precise point positioning (PPP). Numéro de notice : A2022-792 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3390/rs14205222 Date de publication en ligne : 19/10/2022 En ligne : https://doi.org/10.3390/rs14205222 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101909 [article]

PPP rapid ambiguity resolution using Android GNSS raw measurements with a low-cost helical antenna / Xingxing Li in Journal of geodesy, vol 96 n° 10 (October 2022)  

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Accuracy of GNSS RTK/NRTK height difference measurement / Robert Krzyzek in Applied geomatics, vol 14 n° 3 (September 2022)  

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Ambiguity resolution for smartphone GNSS precise positioning: effect factors and performance / Bofeng Li in Journal of geodesy, vol 96 n° 9 (September 2022)  

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Integrating post-processing kinematic (PPK) structure-from-motion (SfM) with unmanned aerial vehicle (UAV) photogrammetry and digital field mapping for structural geological analysis / Daniele Cirillo in ISPRS International journal of geo-information, vol 11 n° 8 (August 2022)  

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Evaluation of QZSS orbit and clock products for real-time positioning applications / Brian Bramanto in Journal of applied geodesy, vol 16 n° 3 (July 2022)  

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Multi-frequency phase-only PPP-RTK model applied to BeiDou data / Pengyu Hou in GPS solutions, vol 26 n° 3 (July 2022)  

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Estimation a priori de l’incertitude altimétrique des positionnements GNSS en RTK ou en statique post-traité : existe-t-il un modèle ? / Thomas Touzé in XYZ, n° 171 (juin 2022)

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An algorithm to assist the robust filter for tightly coupled RTK/INS navigation system / Zun Niu in Remote sensing, vol 14 n° 10 (May-2 2022)  

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Galileo tient enfin ses promesses / Laurent Polidori in Géomètre, n° 2202 (mai 2022)

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Assessment of RTK quadcopter and structure-from-motion photogrammetry for fine-scale monitoring of coastal topographic complexity / Stéphane Bertin in Remote sensing, vol 14 n° 7 (April-1 2022)  

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