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Multi‑constellation GNSS interferometric reflectometry for the correction of long-term snow height retrieval on sloping topography / Wei Zhou in GPS solutions, vol 26 n° 4 (October 2022)
[article]
Titre : Multi‑constellation GNSS interferometric reflectometry for the correction of long-term snow height retrieval on sloping topography Type de document : Article/Communication Auteurs : Wei Zhou, Auteur ; Liangke Huang, Auteur ; Bing Ji, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 140 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] hauteur (coordonnée)
[Termes IGN] manteau neigeux
[Termes IGN] pente
[Termes IGN] Ransac (algorithme)
[Termes IGN] rapport signal sur bruit
[Termes IGN] réflectométrie par GNSS
[Termes IGN] signal GNSS
[Termes IGN] système de référence altimétrique
[Termes IGN] topographie locale
[Termes IGN] transformation en ondelettes
[Termes IGN] valeur aberrante
[Vedettes matières IGN] AltimétrieRésumé : (auteur) Snow is a key parameter for global climate and hydrological systems. Global Navigation Satellite System interferometric reflectometry (GNSS-IR) has been applied to accurately monitor snow height (SH) with low cost and high temporal–spatial resolution. We proposed an improved GNSS-IR method using detrended signal-to-noise ratio (δSNR) arcs corresponding to multipath reflection tracks with different azimuths. After using wavelet decomposition and random sample consensus, noise with various frequencies for SNR arcs and outliers of reflector height (RH) estimations have been sequentially mitigated to enhance the availability of the proposed method. Thus, a height datum based on the ground RHs retrieved from multi-GNSS SNR data is established to compensate for the influence of topography variation with different azimuths in SH retrieval. The approximately 3-month δSNR datasets collected from three stations deployed on sloping topography were used to retrieve SH and compared with the existing method and in situ measurements. The results show that the root mean square errors of the retrievals derived from the proposed method for the three sites are between 4 and 8 cm, and the corresponding correlation surpasses 0.95 when compared to the reference SH datasets. Additionally, we compare the performance of a retrieval with the existing GNSS-IR Web App, and it shows an improvement in RMSE of about 7 cm. Furthermore, because topography variation has been considered, the average correction of SH retrievals is between 2 and 4 cm. The solution with the proposed method helps develop the applications of the GNSS-IR technique on complex topography. Numéro de notice : A2022-712 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-022-01333-0 Date de publication en ligne : 15/09/2022 En ligne : https://doi.org/10.1007/s10291-022-01333-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101590
in GPS solutions > vol 26 n° 4 (October 2022) . - n° 140[article]Potential and limitation of PlanetScope images for 2-D and 3-D Earth surface monitoring with example of applications to glaciers and earthquakes / Saif Aati in IEEE Transactions on geoscience and remote sensing, vol 60 n° 10 (October 2022)
[article]
Titre : Potential and limitation of PlanetScope images for 2-D and 3-D Earth surface monitoring with example of applications to glaciers and earthquakes Type de document : Article/Communication Auteurs : Saif Aati , Auteur ; Jean-Philippe Avouac, Auteur ; Ewelina Rupnik , Auteur ; Marc Pierrot-Deseilligny , Auteur Année de publication : 2022 Article en page(s) : n° 4512919 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] analyse de scène 3D
[Termes IGN] artefact
[Termes IGN] image PlanetScope
[Termes IGN] modèle de déformation des images
[Termes IGN] modèle par fonctions rationnelles
[Termes IGN] séisme
[Termes IGN] surveillance géologiqueRésumé : (auteur) The Planet PlanetScope (PS) CubeSat constellation acquires high-resolution optical images that cover the entire surface of the Earth daily, enabling an unprecedented capability to monitor the Earth’s surface changes. However, our analysis reveals artifacts of the geometry of PS images related to the imaging system and processing issues, limiting the usability of these data for various Earth science applications, including the monitoring of glaciers, dune motion, or the measurement of ground deformation due to earthquakes and landslides. Here, we analyze these artifacts and propose ways to remediate them. We use two examples to evaluate the data and assess the performance of our proposed approaches. The first is the ground deformation caused by the 2019 Ridgecrest earthquake sequence, California, USA, and the second is the 2018–2019 surge of the Shisper glacier in the Karakorum. Using an image correlation technique, we show that PS images exhibit several geometric artifacts, such as scene-to-scene misregistration, inconsistence geolocation accuracy between spectral bands, and topographic artifacts. Altogether, these artifacts make a quantitative analysis of ground displacement difficult and inaccurate. We present a method that remediates most of these geometric artifacts. In addition, we propose a framework for selecting the most appropriate images and a procedure for refining the rational function model (RFM) of unrectified images to monitor surface displacements and topography changes in 3-D. These tools should enhance the use of PS images for Earth science applications. Numéro de notice : A2022-951 Affiliation des auteurs : UGE-LASTIG+Ext (2020- ) Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2022.3215821 Date de publication en ligne : 19/10/2022 En ligne : https://doi.org/10.1109/TGRS.2022.3215821 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103278
in IEEE Transactions on geoscience and remote sensing > vol 60 n° 10 (October 2022) . - n° 4512919[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)
[article]
Titre : PPP rapid ambiguity resolution using Android GNSS raw measurements with a low-cost helical antenna Type de document : Article/Communication Auteurs : Xingxing Li, Auteur ; Hao Wang, Auteur ; Xin Li, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 65 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Androïd
[Termes IGN] antenne
[Termes IGN] données GNSS
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] positionnement ponctuel précis
[Termes IGN] précision du positionnement
[Termes IGN] rapport signal sur bruit
[Termes IGN] résolution d'ambiguïté
[Termes IGN] téléphone intelligentRésumé : (auteur) The release of GNSS raw measurement acquisition privileges on Google Android makes high-precision positioning on the low-cost smart devices possible. However, influenced by the inner linearly polarized antenna, the pseudorange and carrier phase noises of the smart device are much larger than those of the geodetic receiver. As a result, only meter-level positioning accuracy can be obtained based on the smart device’s original antenna. With the external survey-grade antenna enhancing, positioning accuracy of decimeter-level to centimeter-level can be obtained, but it still takes tens of minutes to converge and fix the ambiguity. However, a PPP-RTK method is proposed to achieve rapid integer ambiguity resolution (AR) with the regional atmospheric augmentation. In this contribution, an uncombined PPP-RTK model is developed using Android GNSS raw measurements with an external antenna, after carefully considering the coexistence of single- and dual-frequency signals on smart devices. A low-cost helical antenna is employed to enhance the Android GNSS data as it is capable to provide observation data of comparable quality with the survey-grade antenna and has several advantages of low weight, low-power consumption, and portability. Moreover, a series of quality control methods in the data preprocessing and ambiguity resolution are proposed for smartphone-based PPP-RTK to enhance the positioning results. To validate the proposed method, several experiments are carried out using raw measurements of Xiaomi Mi8 with an external low-cost helical antenna. The result shows that the ambiguity fixed solution can be obtained within 3 min in both static and kinematic scenarios. After the ambiguity resolution, centimeter-level positioning accuracy of (1.7, 2.1, 4.1) cm and (7.2, 4.5, 8.1) cm for the east, north, and up components can be achieved in static and kinematic scenarios, respectively. Numéro de notice : A2022-735 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01661-6 Date de publication en ligne : 27/09/2022 En ligne : https://doi.org/10.1007/s00190-022-01661-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101706
in Journal of geodesy > vol 96 n° 10 (October 2022) . - n° 65[article]Precise onboard time synchronization for LEO satellites / Florian Kunzi in Navigation : journal of the Institute of navigation, vol 69 n° 3 (Fall 2022)
[article]
Titre : Precise onboard time synchronization for LEO satellites Type de document : Article/Communication Auteurs : Florian Kunzi, Auteur ; Oliver Montenbruck, Auteur Année de publication : 2022 Article en page(s) : n° 531 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales
[Termes IGN] données GNSS
[Termes IGN] horloge
[Termes IGN] orbite basse
[Termes IGN] orbitographie
[Termes IGN] oscillateur
[Termes IGN] récepteur DORIS
[Termes IGN] récepteur GNSS
[Termes IGN] récepteur trifréquence
[Termes IGN] synchronisation
[Termes IGN] temps réelRésumé : (auteur) Onboard time synchronization is an important requirement for a wide range of low Earth orbit (LEO) missions such as altimetry or communication services, and extends to future position, navigation, and timing (PNT) services in LEO. For GNSS-based time synchronization, continuous knowledge about the satellite’s position is required and, eventually, the quality of the position solution defines the timing precision attainable through GNSS measurements. Previous research has shown that real-time GNSS orbit determination of LEO satellites can achieve decimeter-level accuracy. This paper characterizes the performance of GNSS-based real-time clock synchronization in LEO using the satellite Sentinel-6A as a real-world case study. The satellite’s ultra-stable oscillator (USO) and triple-frequency GPS/Galileo receiver provide measurements for a navigation filter representative of real-time onboard processing. Continuous evaluation of actual flight data over 14 days shows that a 3D orbit root-mean-square (RMS) error of 11 cm and a 0.9-ns clock standard deviation can be achieved. Numéro de notice : A2022-822 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.531 Date de publication en ligne : 12/04/2022 En ligne : https://doi.org/10.33012/navi.531 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101991
in Navigation : journal of the Institute of navigation > vol 69 n° 3 (Fall 2022) . - n° 531[article]Spherical harmonic synthesis of area-mean potential values on irregular surfaces / Blažej Bucha in Journal of geodesy, vol 96 n° 10 (October 2022)
[article]
Titre : Spherical harmonic synthesis of area-mean potential values on irregular surfaces Type de document : Article/Communication Auteurs : Blažej Bucha, Auteur Année de publication : 2022 Article en page(s) : n° 68 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de gravitation
[Termes IGN] convergence
[Termes IGN] harmonique sphérique
[Termes IGN] surface hétérogène
[Termes IGN] transformation de Legendre
[Termes IGN] transformation rapide de FourierRésumé : (auteur) We present a method to integrate external solid spherical harmonic expansions at geographical grids residing on undulated surfaces. It can be used to evaluate area-mean potential values on planetary surfaces that vary within grid cells. This is in contrast with available methods, which assume cells with a constant spherical radius only. When formulating the technique, we took advantage of 2D spherical Fourier methods to improve the computational speed. The price to be paid are high memory requirements, even with moderate maximum harmonic degrees such as 100 (both of the potential and of the irregular surface). In numerical experiments, we validate the method against independent area-mean potential values to prove its correctness. A study of the series behavior below the sphere of convergence shows that the series may diverge on planetary topographies, similarly as it is with its point-value counterpart. The method can be utilized in numerical studies of the change of boundary method, one of the pivotal concepts of recent high-degree models such as EGM2008. A numerical implementation is made available through CHarm, a C library to work with spherical harmonics up to high degrees. CHarm is accessible via https://github.com/blazej-bucha/charm. Numéro de notice : A2022-736 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01658-1 Date de publication en ligne : 27/09/2022 En ligne : https://doi.org/10.1007/s00190-022-01658-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101708
in Journal of geodesy > vol 96 n° 10 (October 2022) . - n° 68[article]The use of gravity data to determine orthometric heights at the Hong Kong territories / Albertini Nsiah Ababio in Journal of applied geodesy, vol 16 n° 4 (October 2022)PermalinkToward BDS/Galileo/GPS/QZSS triple-frequency PPP instantaneous integer ambiguity resolutions without atmosphere corrections / Jun Tao in GPS solutions, vol 26 n° 4 (October 2022)PermalinkComparing Landsat-8 and Sentinel-2 top of atmosphere and surface reflectance in high latitude regions: case study in Alaska / Jiang Chen in Geocarto international, vol 37 n° 20 ([20/09/2022])PermalinkDense mantle flows periodically spaced below ocean basins / Isabelle Panet in Earth and planetary science letters, vol 594 (15 September 2022)PermalinkEstimation of swell height using spaceborne GNSS-R data from eight CYGNSS satellites / Yanli Zheng in Remote sensing, vol 14 n° 18 (September-2 2022)PermalinkAccuracy of GNSS RTK/NRTK height difference measurement / Robert Krzyzek in Applied geomatics, vol 14 n° 3 (September 2022)PermalinkAdaptive block modeling of time dependent variations of datum reference points in a tectonically active area / Chun-Yun Chou in Survey review, vol 54 n° 386 (September 2022)PermalinkAmbiguity resolution for smartphone GNSS precise positioning: effect factors and performance / Bofeng Li in Journal of geodesy, vol 96 n° 9 (September 2022)PermalinkAutomated detection of discontinuities in EUREF permanent GNSS network stations due to earthquake events / Sergio Baselga in Survey review, vol 54 n° 386 (September 2022)PermalinkLe cheminement du douzième parallèle (deuxième partie) : article tiré de Jalon, bulletin de l’association des personnels retraités de l’IGN, n° 146-bis de mai 2022 / Jean-Claude Leblanc in XYZ, n° 172 (septembre 2022)Permalink