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BDS and GPS side-lobe observation quality analysis and orbit determination with a GEO satellite onboard receiver / Wenwen Li in GPS solutions, vol 27 n° 1 (January 2023)  

Public [article]  inGPS solutions > vol 27 n° 1 (January 2023) . - n° 18 Titre : BDS and GPS side-lobe observation quality analysis and orbit determination with a GEO satellite onboard receiver Type de document : Article/Communication Auteurs : Wenwen Li, Auteur ; Kecai Jiang, Auteur ; Min Li, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 18 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] code GNSS [Termes IGN] orbite géostationnaire [Termes IGN] orbite précise [Termes IGN] orbitographie [Termes IGN] orbitographie par GNSS [Termes IGN] phase [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par GPS Résumé : (auteur) Multi-GNSS combination can alleviate problems associated with GNSS-based geostationary earth orbit (GEO) satellite navigation and orbit determination (OD), such as GNSS availability and observation geometry deterioration. However, only GPS has been widely applied and investigated in GEO missions, whereas GEO OD with BDS requires further exploration. The Chinese GEO satellite TJS-5, equipped with a GPS and BDS-compatible receiver, is the first GEO mission that tracks both BDS 2nd and 3rd generation satellites since BDS global deployment. With the TJS-5 real onboard data, we evaluate BDS side-lobe signal performance and the BDS contribution to GEO OD. Due to transmit antenna gain deficiencies in the side lobes, BDS shows a worse tracking performance than GPS with an average satellite number of 4.3 versus 7.8. Both GPS and BDS reveal inconsistency between carrier-phase and code observations, which reaches several meters and significantly degrades post-dynamic OD calculation. We estimate the consistency as a random walk process in the carrier-phase observation model to reduce its impact. With inconsistency estimated, the post-fit carrier-phase residuals decrease from 0.21 to 0.09 m for both GPS and BDS. The OD precision is significantly improved, from 1.95 to 1.42 m with only GPS and from 3.14 to 2.71 m with only BDS; the GPS and BDS combined OD exhibits the largest improvement from 1.74 to 0.82 m, demonstrating that adding BDS improves the OD precision by 43.3%. The above results indicate that the proposed carrier-phase inconsistency estimation approach is effective for both GPS and BDS and can achieve an orbit precision within 1.0 m using multi-GNSS measurements. Numéro de notice : A2023-026 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01358-5 Date de publication en ligne : 06/11/2022 En ligne : https://doi.org/10.1007/s10291-022-01358-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102261 [article]

GENESIS: co-location of geodetic techniques in space / Pacôme Delva in Earth, Planets and Space, vol 75 n° 1 (2023)  

Public [article]  inEarth, Planets and Space > vol 75 n° 1 (2023) . - n° 5 (2023) Titre : GENESIS: co-location of geodetic techniques in space Type de document : Article/Communication Auteurs : Pacôme Delva, Auteur ; Zuheir Altamimi , Auteur ; et al., Auteur ; Laurent Métivier , Auteur Année de publication : 2023 Article en page(s) : n° 5 (2023) Note générale : bibliographie by Pacôme Delva, Zuheir Altamimi, Alejandro Blazquez, Mathis Blossfeld, Johannes Böhm, Pascal Bonnefond, Jean-Paul Boy, Sean Bruinsma, Grzegorz Bury, Miltiadis Chatzinikos, Alexandre Couhert, Clément Courde, Rolf Dach, Véronique Dehant, Simone Dell’Agnello, Gunnar Elgered, Werner Enderle, Pierre Exertier, Susanne Glaser, Rüdiger Haas, Wen Huang, Urs Hugentobler, Adrian Jäggi, Ozgur Karatekin, Frank G. Lemoine, Christophe Le Poncin-Lafitte, Susanne Lunz, Benjamin Männel, Flavien Mercier, Laurent Métivier, Benoît Meyssignac, Jürgen Müller, Axel Nothnagel, Felix Perosanz, Roelof Rietbroek, Markus Rothacher, Harald Schuh, Hakan Sert, Krzysztof Sosnica, Paride Testani, Javier Ventura-Traveset, Gilles Wautelet & Radoslaw Zajdel  Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] co-positionnement [Termes IGN] géodésie spatiale [Termes IGN] International Terrestrial Reference Frame [Termes IGN] précision du positionnement [Termes IGN] satellite de positionnement Résumé : (auteur) Improving and homogenizing time and space reference systems on Earth and, more specifically, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1 mm and a long-term stability of 0.1 mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, such as those located at tide gauges, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation, contributing to a better understanding of natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities, including the International Association of Geodesy (IAG), which has enunciated geodesy requirements for Earth sciences. Moreover, the United Nations Resolution 69/266 states that the full societal benefits in developing satellite missions for positioning and Remote Sensing of the Earth are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology. This paper has been written and supported by a large community of scientists from many countries and working in several different fields of science, ranging from geophysics and geodesy to time and frequency metrology, navigation and positioning. As it is explained throughout this paper, there is a very high scientific consensus that the GENESIS mission would deliver exemplary science and societal benefits across a multidisciplinary range of Navigation and Earth sciences applications, constituting a global infrastructure that is internationally agreed to be strongly desirable. Numéro de notice : A2023-078 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1186/s40623-022-01752-w Date de publication en ligne : 11/01/2023 En ligne : https://doi.org/10.1186/s40623-022-01752-w Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102519 [article]

Precise orbit determination for BDS-3 GEO satellites enhanced by intersatellite links / Xiaojie Li in GPS solutions, vol 27 n° 1 (January 2023)  

Public [article]  inGPS solutions > vol 27 n° 1 (January 2023) . - n° 8 Titre : Precise orbit determination for BDS-3 GEO satellites enhanced by intersatellite links Type de document : Article/Communication Auteurs : Xiaojie Li, Auteur ; Xiaogong Hu, Auteur ; Rui Guo, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 8 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] constellation BeiDou [Termes IGN] décalage d'horloge [Termes IGN] orbite géostationnaire [Termes IGN] orbite précise [Termes IGN] orbitographie [Termes IGN] qualité des données Résumé : (auteur) Geostationary orbit (GEO) satellites are an integral part of the BeiDou Navigation Satellite System (BDS). Precise orbit determination (POD) for GEO satellites is difficult due to their geostationary characteristics. The orbit determination accuracy that can be achieved based on regional tracking stations in China cannot satisfy high-precision service requirements. The third generation of BDS (BDS-3) is the first global navigation satellite system that synergistically uses regional monitoring stations and global intersatellite links (ISLs) to realize global service. In this study, the quality of ISL data is analyzed based on the residuals of the intersatellite clock offset and the observed-minus-computed residuals of the ISL data. The orbit determination accuracy is assessed based on the observation residuals, the multiday consistency of the ISL time delays, overlapping orbit comparison, the user equivalent range error (UERE), and the accuracy of the clock offset. The results show that the ISL measurement noise for the GEO satellites is 3 cm, and the multiday consistency accuracy of the ISL time delay is better than 0.07 ns. Compared to the satellite-to-ground link (SGL)-based orbit determination method, the root mean square (RMS) three-dimensional (3D) position error of the overlapping orbit differences (OODs) is improved from 1.11 to 0.22 m with the combined SGL- and ISL-based method. Simultaneously, the UERE improves from 0.57 to 0.19 m, and the accuracy of the satellite clock offset improves from 1.09 to 0.61 ns. Numéro de notice : A2023-001 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01330-3 Date de publication en ligne : 14/10/2022 En ligne : https://doi.org/10.1007/s10291-022-01330-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101870 [article]

Deep learning detects invasive plant species across complex landscapes using Worldview-2 and Planetscope satellite imagery / Thomas A. Lake in Remote sensing in ecology and conservation, vol 8 n° 6 (December 2022)  

Public [article]  inRemote sensing in ecology and conservation > vol 8 n° 6 (December 2022) . - pp 875 - 889 Titre : Deep learning detects invasive plant species across complex landscapes using Worldview-2 and Planetscope satellite imagery Type de document : Article/Communication Auteurs : Thomas A. Lake, Auteur ; Ryan D. Briscoe Runquist, Auteur ; David A. Moeller, Auteur Année de publication : 2022 Article en page(s) : pp 875 - 889 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] carte d'occupation du sol [Termes IGN] classification par réseau neuronal convolutif [Termes IGN] classification par réseau neuronal récurrent [Termes IGN] espèce exotique envahissante [Termes IGN] image Worldview [Termes IGN] PlanetScope [Termes IGN] série temporelle Résumé : (auteur) Effective management of invasive species requires rapid detection and dynamic monitoring. Remote sensing offers an efficient alternative to field surveys for invasive plants; however, distinguishing individual plant species can be challenging especially over geographic scales. Satellite imagery is the most practical source of data for developing predictive models over landscapes, but spatial resolution and spectral information can be limiting. We used two types of satellite imagery to detect the invasive plant, leafy spurge (Euphorbia virgata), across a heterogeneous landscape in Minnesota, USA. We developed convolutional neural networks (CNNs) with imagery from Worldview-2 and Planetscope satellites. Worldview-2 imagery has high spatial and spectral resolution, but images are not routinely taken in space or time. By contrast, Planetscope imagery has lower spatial and spectral resolution, but images are taken daily across Earth. The former had 96.1% accuracy in detecting leafy spurge, whereas the latter had 89.9% accuracy. Second, we modified the CNN for Planetscope with a long short-term memory (LSTM) layer that leverages information on phenology from a time series of images. The detection accuracy of the Planetscope LSTM model was 96.3%, on par with the high resolution, Worldview-2 model. Across models, most false-positive errors occurred near true populations, indicating that these errors are not consequential for management. We identified that early and mid-season phenological periods in the Planetscope time series were key to predicting leafy spurge. Additionally, green, red-edge and near-infrared spectral bands were important for differentiating leafy spurge from other vegetation. These findings suggest that deep learning models can accurately identify individual species over complex landscapes even with satellite imagery of modest spatial and spectral resolution if a temporal series of images is incorporated. Our results will help inform future management efforts using remote sensing to identify invasive plants, especially across large-scale, remote and data-sparse areas. Numéro de notice : A2023-033 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.1002/rse2.288 En ligne : https://doi.org/10.1002/rse2.288 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102295 [article]

On the relation of GNSS phase center offsets and the terrestrial reference frame scale: a semi-analytical analysis / Oliver Montenbruck in Journal of geodesy, vol 96 n° 11 (November 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 11 (November 2022) . - n° 90 Titre : On the relation of GNSS phase center offsets and the terrestrial reference frame scale: a semi-analytical analysis Type de document : Article/Communication Auteurs : Oliver Montenbruck, Auteur ; Peter Steigenberger, Auteur ; Arturo Villiger, Auteur ; Paul Rebischung , Auteur Année de publication : 2022 Article en page(s) : n° 90 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne GNSS [Termes IGN] centre de phase [Termes IGN] décalage d'horloge [Termes IGN] hauteur (coordonnée) [Termes IGN] International Terrestrial Reference Frame [Termes IGN] orbitographie [Termes IGN] phase [Termes IGN] positionnement par GNSS [Termes IGN] retard troposphérique zénithal [Termes IGN] station GNSS Résumé : (auteur) Phase center offsets (PCOs) of global navigation satellites systems (GNSS) transmit antennas along the boresight axis introduce line-of-sight-dependent range changes in the modeling of GNSS observations that are strongly correlated with the estimated station heights. As a consequence, changes in the adopted PCOs impact the scale of GNSS-based realizations of the terrestrial reference frame (TRF). Vice versa, changes in the adopted TRF scale require corrections to the GNSS transmit antenna PCOs for consistent observation modeling. Early studies have determined an approximate value of α=−0.050 for the ratio of station height changes and satellite PCO changes in GPS orbit determination and phase center adjustment. However, this is mainly an empirical value and limited information is available on the actual PCO-scale relation and how it is influenced by other factors. In view of the recurring need to adjust the IGS antenna models to new ITRF scales, a semi-analytical model is developed to determine values of α for the four current GNSSs from first principles without a need for actual network data processing. Given the close coupling of satellite boresight angle and station zenith angle, satellite PCO changes are essentially compensated by a combination of station height, zenith troposphere delay, and receiver clock offset. As such, the value of α depends not only on the orbital altitude of the considered GNSS but also on the elevation-dependent distribution of GNSS observations and their weighting, as well as the elevation mask angle and the tropospheric mapping function. Based on the model, representative values of αGPS=−0.051, αGLO=−0.055, αGAL=−0.041, and αBDS-3=−0.046 are derived for GPS, GLONASS, Galileo, and BeiDou-3 at a 10∘ elevation cutoff angle. These values may vary by Δα≈0.003 depending on the specific model assumptions and data processing parameters in a precise orbit determination or precise point positioning. Likewise changes of about ±0.003 can be observed when varying the cutoff angle between 5∘ and 15∘. Numéro de notice : A2022-836 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-022-01678-x Date de publication en ligne : 09/11/2022 En ligne : https://doi.org/10.1007/s00190-022-01678-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102033 [article]

Precise onboard time synchronization for LEO satellites / Florian Kunzi in Navigation : journal of the Institute of navigation, vol 69 n° 3 (Fall 2022)  

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Pyeo: A Python package for near-real-time forest cover change detection from Earth observation using machine learning / J.F. Roberts in Computers & geosciences, vol 167 (October 2022)  

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Result of the MICROSCOPE weak equivalence principle test / Pierre Touboul in Classical and Quantum Gravity, vol 39 n° 20 (October 2022)  

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Comparing 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])  

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Crowdsourcing-based application to solve the problem of insufficient training data in deep learning-based classification of satellite images / Ekrem Saralioglu in Geocarto international, vol 37 n° 18 ([01/09/2022])  

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Landsat, le programme fête ses cinquante ans / Laurent Polidori in Géomètre, n° 2205 (septembre 2022)

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MICROSCOPE Mission: Final Results of the Test of the Equivalence Principle / Pierre Touboul in Physical Review Letters, vol 129 n° 12 ([01/09/2022])  

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A multi-source spatio-temporal data cube for large-scale geospatial analysis / Fan Gao in International journal of geographical information science IJGIS, vol 36 n° 9 (September 2022)  

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Orbit determination, clock estimation and performance evaluation of BDS-3 PPP-B2b service / Chengpan Tang in Journal of geodesy, vol 96 n° 9 (September 2022)  

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Validation of a corner reflector installation at Côte d’Azur multi-technique geodetic observatory / Xavier Collilieux in Advances in space research, vol 70 n° 2 (15 July 2022)  

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