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Cluster-based empirical tropospheric corrections applied to InSAR time series analysis / Kyle Dennis Murray in IEEE Transactions on geoscience and remote sensing, Vol 59 n° 3 (March 2021)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > Vol 59 n° 3 (March 2021) . - pp 2204 - 2212 Titre : Cluster-based empirical tropospheric corrections applied to InSAR time series analysis Type de document : Article/Communication Auteurs : Kyle Dennis Murray, Auteur ; Rowena B. Lohman, Auteur ; David P. S. Bekaert, Auteur Année de publication : 2021 Article en page(s) : pp 2204 - 2212 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] bande C [Termes IGN] bruit atmosphérique [Termes IGN] classification par nuées dynamiques [Termes IGN] déformation de la croute terrestre [Termes IGN] image radar moirée [Termes IGN] image Sentinel-SAR [Termes IGN] Mexique [Termes IGN] retard troposphérique [Termes IGN] série temporelle Résumé : (Auteur) Interferometric synthetic aperture radar (InSAR) allows for mapping of crustal deformation on land with high spatial resolution and precision in areas with high signal-to-noise ratios. Efforts to obtain precise displacement time series globally, however, are severely limited by radar path delays within the troposphere. The tropospheric delay is integrated along the full path length between the ground and the satellite, resulting in correlations between the interferometric phase and elevation that can vary dramatically in both space and time. We evaluate the performance of spatially variable, empirical removal of phase-elevation dependence within SAR interferograms through the use of the K -means clustering algorithm. We apply this method to both synthetic test data, as well as to C-band Sentinel-1a/b time series acquired over a large area in south-central Mexico along the Pacific coast and inland—an area with a large elevation gradient that is of particular interest to researchers studying tectonic- and anthropogenic-related deformation. We show that the clustering algorithm is able to identify cases where tropospheric properties vary across topographic divides, reducing total root mean square (rms) by an average of 50%, as opposed to a spatially constant phase-elevation correction, which has insignificant error reduction. Our approach also reduces tropospheric noise while preserving test signals in synthetic examples. Finally, we show the average standard deviation of the residuals from the best-fit linear rate decreases from approximately 3 to 1.5 cm, which corresponds to a change in the error on the best-fit linear rate from 0.94 to 0.63 cm/yr. Numéro de notice : A2021-215 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2020.3003271 Date de publication en ligne : 30/06/2020 En ligne : https://doi.org/10.1109/TGRS.2020.3003271 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97204 [article]

Precise point positioning with decimetre accuracy using wide-lane ambiguities and triple-frequency GNSS data / Manoj Deo in Journal of applied geodesy, vol 14 n° 3 (July 2020)  

Public [article]  inJournal of applied geodesy > vol 14 n° 3 (July 2020) . - pp 263 – 284 Titre : Precise point positioning with decimetre accuracy using wide-lane ambiguities and triple-frequency GNSS data Type de document : Article/Communication Auteurs : Manoj Deo, Auteur ; Ahmed El-Mowafy, Auteur Année de publication : 2020 Article en page(s) : pp 263 – 284 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] ambiguïté entière [Termes IGN] bruit atmosphérique [Termes IGN] combinaison linéaire [Termes IGN] données GNSS [Termes IGN] phase [Termes IGN] positionnement ponctuel précis [Termes IGN] triple différence Résumé : (auteur) This paper proposes precise point positioning (PPP) methods that offer an accuracy of a few decimetres (dm) with triple frequency GNSS data. Firstly, an enhanced triple frequency linear combination is presented for rapid fixing of the extra wide-lane (EWL) and wide-lane (WL) ambiguities for GPS, Beidou-2 and Galileo. This has improved performance compared to the Melbourne-Wübbena (MW) linear combination, and has 6.7 % lower measurement noise for the GPS L1/L2 signals, 12.7 % for L1/L5 and 0.7 % for L2/L5. Analysis with tested data showed a 5–6 % reduction in time required to fix the N21 and N51 ambiguities. Once the EWL/WL ambiguities are fixed with the proposed linear combinations, three methods are presented that aim to provide positioning accuracy of a few dm. In the first approach, the three EWL/WL ambiguities in their respective phase equations are used to derive a low-noise ionosphere-free (IF) linear combination. The second method uses a low noise IF combination with two carrier-phase EWL/WL equations and a single pseudorange measurement. The third method uses a low noise IF combination with a single carrier phase EWL equation and two pseudorange measurements. These proposed methods can provide dm level positioning accuracy if carrier phase measurements with mm precision is tracked by the receiver. When comparing these combinations with a combination proposed in [], it is found that superior performance is achieved with the third method when carrier phase noise is >5–6 mm for GPS and Beidou-2 and >2–3 mm for Galileo. This model only requires the EWL ambiguity to be fixed which typically takes just one epoch of data. Thus, the user achieves instant decimetre level PPP accuracy. Numéro de notice : A2020-466 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2019-0068 Date de publication en ligne : 11/03/2020 En ligne : https://doi.org/10.1515/jag-2019-0068 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95432 [article]

Performance of Galileo precise time and frequency transfer models using quad-frequency carrier phase observations / Pengfei Zhang in GPS solutions, vol 24 n° 2 (April 2020)  

Public [article]  inGPS solutions > vol 24 n° 2 (April 2020) Titre : Performance of Galileo precise time and frequency transfer models using quad-frequency carrier phase observations Type de document : Article/Communication Auteurs : Pengfei Zhang, Auteur ; Rui Tu, Auteur ; Yuping Gao, Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] bruit atmosphérique [Termes IGN] décalage d'horloge [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] fréquence multiple [Termes IGN] modèle mathématique [Termes IGN] phase [Termes IGN] positionnement ponctuel précis [Termes IGN] signal BeiDou [Termes IGN] signal Galileo [Termes IGN] signal GLONASS [Termes IGN] signal GNSS [Termes IGN] signal GPS [Termes IGN] temps-fréquence [Termes IGN] transmission de données Résumé : (auteur) GNSSs, such as Galileo and modernized GPS, BeiDou and GLONASS systems, offer new potential and challenges in precise time and frequency transfer using multi-frequency observations. We focus on the performance of Galileo time and frequency transfer using the E1, E5a, E5b and E5 observations. Dual-frequency, triple-frequency and quad-frequency models for precise time and frequency transfer with different Galileo observations are proposed. Four time and transfer links between international time laboratories are used to assess the performances of different models in terms of time link noise level and frequency stability indicators. The average RMS values of the smoothed residuals of the clock difference series are 0.033 ns, 0.033 ns and 0.034 ns for the dual-frequency, triple-frequency and quad-frequency models with four time links, respectively. With respect to frequency stability, the average stability values at 15,360 s are 9.51 × 10−15, 9.46 × 10−15 and 9.37 × 10−15 for the dual-frequency, triple-frequency and quad-frequency models with four time links, respectively. Moreover, although biases among different models and receiver the inter-frequency exist, their characteristics are relatively stable. Generally, the dual-/triple-/quad-frequency models show similar performance for those time links, and the quad-frequency models can provide significant potential for switching among and unifying the three multi-frequency solutions, as well as further enhancing the redundancy and reliability compared to the current dual-frequency time transfer method. Numéro de notice : A2020-083 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-0955-7 Date de publication en ligne : 04/02/2020 En ligne : https://doi.org/10.1007/s10291-020-0955-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94652 [article]

RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications / Francesco Darugna (2019)

Public Titre : RTK and PPP-RTK using smartphones: From short-baseline to long-baseline applications Type de document : Article/Communication Auteurs : Francesco Darugna, Auteur ; et al., Auteur Editeur : Alexandria : Institute of Navigation Année de publication : 2019 Conférence : ION GNSS+ 2019, 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation 01/09/2019 Miami Floride - Etats-Unis non OA proceedings Importance : pp 3932 - 3945 Format : 21 x 30 cm Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] bruit atmosphérique [Termes IGN] correction du trajet multiple [Termes IGN] ligne de base [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] précision centimétrique [Termes IGN] téléphone intelligent [Termes IGN] trajet multiple Résumé : (auteur) Low cost receivers providing GNSS code and phase raw measurements for multiple frequencies and multiple GNSS constellations have recently become available on the market. This significantly increases the number of devices equipped with the necessary sensors to perform precise GNSS positioning like Network-RTK or PPP. The smartphone GNSS measurements often suffer from low signal-to-noise, inhomogeneous antenna gain and high levels of multipath. Here, we show how to tackle several of currently present obstacles and demonstrate centimeter-level kinematic positioning with a low-cost GNSS antenna and a low-cost GNSS receiver built into an off-the-shelf smartphone. For some devices we found that the phase observations do not have integer characteristic but appear to have random biases. To some extend these observations can still be used in a “float”-type precise algorithm. Low cost GNSS sensors like the ones built into smartphones are generally used with antennas that have a uniform gain pattern and do not reject LHCP signals. Accordingly, strong multipath influence is observed in many applications. Experiments both in a zero-baseline and a short-baseline configuration have been performed, to evaluate the aforementioned biases and discontinuities. We demonstrate instantaneous ambiguity resolution in the zero-baseline setup, showing the potential for RTK-positioning with low-cost sensors available inside smartphones. Positioning with PPP-RTK or Network-RTK is more challenging because additional residual atmospheric noise is present. Experiments with different baseline lengths have been performed in different ionospheric conditions and the achieved accuracies are reported. Numéro de notice : C2019-040 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95376

Reduction of PPP convergence period through pseudorange multipath and noise mitigation / Garrett Seepersad in GPS solutions, vol 19 n° 3 (July 2015)  

Public [article]  inGPS solutions > vol 19 n° 3 (July 2015) . - pp 369 - 379 Titre : Reduction of PPP convergence period through pseudorange multipath and noise mitigation Type de document : Article/Communication Auteurs : Garrett Seepersad, Auteur ; Sunil Bisnath, Auteur Année de publication : 2015 Article en page(s) : pp 369 - 379 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] bruit atmosphérique [Termes IGN] correction du trajet multiple [Termes IGN] filtrage du bruit [Termes IGN] mesurage de pseudo-distance [Termes IGN] positionnement ponctuel précis [Termes IGN] trajet multiple Résumé : (auteur) Pseudorange multipath and pseudorange noise are the largest remaining unmanaged error sources in PPP. It is proposed that by reducing the effects of multipath and noise on the pseudorange observable, accurate estimates of carrier phase float ambiguities will be attained sooner, thus reducing the initial convergence period of PPP. Given the problem, this study seeks to improve mitigation of the pseudorange errors. The well-known multipath linear combination is used in two distinct ways: (1) to directly correct the raw pseudorange observables and (2) to stochastically de-weight the pseudorange observables. The improvements in the solution were calculated with respect to the conventional GPS PPP float solution, where the raw pseudorange observables were not modified or stochastically de-weighted. Corrections to the observables were made using the multipath linear combination from data obtained from the previous and same day. Minimal improvements were noted using the multipath observable from the previous day. Using the multipath observable from the same day was possible in real-time and post-processing modes, showing an improvement in the rate of convergence for 48 and 57 % of the data, respectively. An improvement in the rate of convergence for 34 % of the data was observed when the pseudorange measurements were stochastically de-weighted using the multipath observable. Datasets with no improvements from directly correcting the raw pseudorange observables (43 %) or stochastically de-weighting the pseudorange observables (66 %) presented similar quality of results as the conventional PPP solution. Numéro de notice : A2015-461 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-03 Date de publication en ligne : 01/08/2014 En ligne : https://doi.org/10.1007/s10291-014-0395-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=77136 [article]

Essential Earth imaging for GIS / Lawrence Fox III (2015)

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Evaluation des performances de capteurs topographiques pour la mesure de déformation / Julien Assémat (2015)    

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Simultaneous denoising and intrinsic order selection in hyperspectral imaging / M. Farzam in IEEE Transactions on geoscience and remote sensing, vol 49 n° 9 (September 2011)  

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Scanning geometry: Influencing factor on the quality of terrestrial laser scanning points / S. Soudarissanane in ISPRS Journal of photogrammetry and remote sensing, vol 66 n° 4 (July - August 2011)  

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A model-based approach to semi-automated reconstruction of buildings from aerial images / Kourosh Khoshelham in Photogrammetric record, vol 19 n° 106 (June - August 2004)  

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Atmospheric corrections for remote sensing / E.M. Rollin (1985)

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Correction de l'influence de l'atmosphère sur des données acquises en télédétection des ressources terrestres / M.C. Rouquet (1984)

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