Centre dedocumentation
scientifique

An improved vertical correction method for the inter-comparison and inter-validation of Integrated Water Vapour measurements / Olivier Bock in Atmospheric measurement techniques, vol 15 n° inconnu ([01/04/2022])  

Public [article]  inAtmospheric measurement techniques > vol 15 n° inconnu [01/04/2022] Titre : An improved vertical correction method for the inter-comparison and inter-validation of Integrated Water Vapour measurements Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Pierre Bosser , Auteur ; Carl Mears, Auteur Année de publication : 2022 Projets : VEGAN / Bock, Olivier Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] correction des altitudes [Termes IGN] données GPS [Termes IGN] données météorologiques [Termes IGN] erreur systématique [Termes IGN] montagne [Termes IGN] régression multiple [Termes IGN] teneur intégrée en vapeur d'eau [Termes IGN] zone intertropicale Résumé : (auteur) Integrated Water Vapour (IWV) measurements from similar or different techniques are often inter-compared for calibration and validation purposes. Results are usually assessed in terms of bias (difference of the means), standard deviation of the differences, and linear fit slope and offset (intercept) estimates. When the instruments are located at different elevations, a correction must be applied to account for the vertical displacement between the sites. Empirical formulations are traditionally used for this correction. In this paper, we show that the widely-used correction model based on a standard, exponential, profile for water vapour cannot properly correct the bias, slope, and offset parameters simultaneously. Correcting the bias with this model degrades the slope and offset estimates, and vice-versa. This paper proposes an improved correction model which overcomes these limitations. The model uses a multi-linear regression of slope and offset parameters from a radiosonde climatology. It is able to predict monthly parameters with a root-mean-square error smaller than 0.5 kg m-2 for height differences up to 500 m. The method is applied to the inter-comparison of GPS IWV data in a tropical mountainous area and to the inter-validation of GPS and satellite microwave radiometer data. This paper also emphasizes the need for using a slope and offset regression method that accounts for errors in both variables and for correctly specifying these errors. Numéro de notice : A2022-327 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/amt-2022-40 Date de publication en ligne : 21/04/2022 En ligne : https://doi.org/10.5194/amt-2022-40 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100492 [article]

Seasonal variations of vertical crustal motion in Australia observed by joint analysis of GPS and GRACE / Hao Wang in Geomatics and Information Science of Wuhan University, vol 47 n° 2 (February 2022)  

Public [article]  inGeomatics and Information Science of Wuhan University > vol 47 n° 2 (February 2022) . - pp 197 - 207 Titre : Seasonal variations of vertical crustal motion in Australia observed by joint analysis of GPS and GRACE Type de document : Article/Communication Auteurs : Hao Wang, Auteur ; Jianping Yue, Auteur ; Yunfei Xiang, Auteur Année de publication : 2022 Article en page(s) : pp 197 - 207 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse de spectre singulier [Termes IGN] Australie [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] données GPS [Termes IGN] données GRACE [Termes IGN] transformation en ondelettes [Termes IGN] variation saisonnière Résumé : (auteur) Objectives There are obvious seasonal variations in the GPS height time series, which affect the improvement of precision and can be corrected by both mathematical modelling and geophysical mechanisms. Compared to least square fitting, singular spectrum analysis (SSA) can extract random seasonal signals effectively through signal reconstruction, which is unaffected by the assumed sinusoidal waves. According to the elastic loading theory, the gravity recovery and climate experiment (GRACE) can be used to calculate the vertical surface displacement caused by changes in terrestrial water storage. Methods This paper mainly studies the feasibility of correcting the seasonal variations in GPS heights using SSA and GRACE inversion results. The height time series of 27 GPS stations in Australia with a time span of from 5 to 10 years were chosen and combined with GRACE simultaneous inversions. Results Because the spatial resolutions of GRACE are coarse and the loading displacement is much more sensitive to near-field mass changes than far-field ones, the amplitudes of GRACE-inferred hydrological loading deformations are significantly smaller than GPS. The weighted root mean square (WRMS) are reduced at 22 stations after GRACE-inferred displacement corrections, and the correlation coefficients between deformations estimated by GPS and GRACE range from 0.12 to 0.78 with a mean value of 0.43, indicating that GPS and GRACE results have good consistency and correlation. SSA is used to extract the annual signals of vertical displacements derived from GPS and GRACE, and contribution rates of singular spectral variance of annual signals are 21.60% and 34.48%, respectively, expressing that annual signals are the main components of GRACE-inferred results. Geographical climatic conditions have a significant impact on the consistency of annual signals derived from GPS and GRACE. Compared with the arid areas in central and western Australia, the amplitude and phase of annual signals derived from GPS and GRACE are more consistent in the northern region with seasonal rainfall. Furthermore, cross wavelet transform (XWT) finds that the vertical displacement series derived from GPS and GRACE of each station have a significant resonance period of one year. The circular average phase angles of GPS/GRACE at the period closet to 1 cycle per year (cpy) outside the cone of influence range from -74.03° to 67.23°. The mean XWT-based semblances range from 0.28 to 0.99 with an average value of 0.79, showing that there is a significant positive correlation between the annual variations derived from GPS and GRACE. Conclusions Overall, GRACE-inferred deformations can explain the annual variations of GPS-derived displacements, particularly in areas with high hydrological loading. It is possible to correct the annual signals of GPS heights by GRACE inversions, but the effect is not as good as the SSA-filtered annual signals. Numéro de notice : A2022-150 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.13203/j.whugis20190282 Date de publication en ligne : 05/02/2022 En ligne : http://dx.doi.org/10.13203/j.whugis20190282 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100109 [article]

Impact of observation sampling rate on multi-GNSS static PPP performance / Berkay Bahadur in Survey review, Vol 53 n° 378 (May 2021)  

Public [article]  inSurvey review > Vol 53 n° 378 (May 2021) . - pp 206 - 215 Titre : Impact of observation sampling rate on multi-GNSS static PPP performance Type de document : Article/Communication Auteurs : Berkay Bahadur, Auteur ; Metin Nohutcu, Auteur Année de publication : 2021 Article en page(s) : pp 206 - 215 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] données GLONASS [Termes IGN] données GNSS [Termes IGN] données GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] positionnement statique [Termes IGN] taux d'échantillonnage [Termes IGN] temps de convergence [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) The main objective of this study is to investigate the impact of observation sampling rate on the PPP performance, in terms of positioning accuracy and convergence time, under different multi-GNSS combinations. For this purpose, daily observation datasets collected at ten IGS-MGEX (International GNSS Service-Multi-GNSS Experiment) stations during the 1-week period of January 6-12, 2019 with 1-s, 5-s,15-s, and 30-s sampling rates were processed under three different PPP processing modes, namely GPS-only, GPS/GLONASS and multi-GNSS. The results indicate that the use of high-rate observation sampling improves the PPP performance for all processing modes significantly. The contribution of increasing sampling rate, both for positioning error and convergence time, is more prominent in shorter periods, especially within the first 30 min for all processing modes. Finally, the multi-GNSS processing mode with the 1-s observation sampling rate has the best PPP performance and offers a considerable prospect for the GNSS applications. Numéro de notice : A2021-403 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2019.1711346 Date de publication en ligne : 12/01/2020 En ligne : https://doi.org/10.1080/00396265.2019.1711346 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97716 [article]

Understanding collective human movement dynamics during large-scale events using big geosocial data analytics / Junchuan Fan in Computers, Environment and Urban Systems, vol 87 (May 2021)  

Public [article]  inComputers, Environment and Urban Systems > vol 87 (May 2021) . - n° 101605 Titre : Understanding collective human movement dynamics during large-scale events using big geosocial data analytics Type de document : Article/Communication Auteurs : Junchuan Fan, Auteur ; Kathleen Stewart, Auteur Année de publication : 2021 Article en page(s) : n° 101605 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes IGN] collecte de données [Termes IGN] données GPS [Termes IGN] données issues des réseaux sociaux [Termes IGN] données localisées des bénévoles [Termes IGN] données massives [Termes IGN] dynamique spatiale [Termes IGN] échantillonnage de données [Termes IGN] éclipse solaire [Termes IGN] estimation par noyau [Termes IGN] Etats-Unis [Termes IGN] événement [Termes IGN] géolocalisation [Termes IGN] migration humaine [Termes IGN] mobilité territoriale [Termes IGN] téléphonie mobile Résumé : (auteur) Conventional approaches for modeling human mobility pattern often focus on human activity and movement dynamics in their regular daily lives and cannot capture changes in human movement dynamics in response to large-scale events. With the rapid advancement of information and communication technologies, many researchers have adopted alternative data sources (e.g., cell phone records, GPS trajectory data) from private data vendors to study human movement dynamics in response to large-scale natural or societal events. Big geosocial data such as georeferenced tweets are publicly available and dynamically evolving as real-world events are happening, making it more likely to capture the real-time sentiments and responses of populations. However, precisely-geolocated geosocial data is scarce and biased toward urban population centers. In this research, we developed a big geosocial data analytical framework for extracting human movement dynamics in response to large-scale events from publicly available georeferenced tweets. The framework includes a two-stage data collection module that collects data in a more targeted fashion in order to mitigate the data scarcity issue of georeferenced tweets; in addition, a variable bandwidth kernel density estimation(VB-KDE) approach was adopted to fuse georeference information at different spatial scales, further augmenting the signals of human movement dynamics contained in georeferenced tweets. To correct for the sampling bias of georeferenced tweets, we adjusted the number of tweets for different spatial units (e.g., county, state) by population. To demonstrate the performance of the proposed analytic framework, we chose an astronomical event that occurred nationwide across the United States, i.e., the 2017 Great American Eclipse, as an example event and studied the human movement dynamics in response to this event. However, this analytic framework can easily be applied to other types of large-scale events such as hurricanes or earthquakes. Numéro de notice : A2021-275 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/SOCIETE NUMERIQUE Nature : Article DOI : 10.1016/j.compenvurbsys.2021.101605 Date de publication en ligne : 05/02/2021 En ligne : https://doi.org/10.1016/j.compenvurbsys.2021.101605 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97358 [article]

1996–2017 GPS position time series, velocities and quality measures for the CORS Network / Jarir Saleh in Journal of applied geodesy, vol 15 n° 2 (April 2021)  

Public [article]  inJournal of applied geodesy > vol 15 n° 2 (April 2021) . - pp 105 - 115 Titre : 1996–2017 GPS position time series, velocities and quality measures for the CORS Network Type de document : Article/Communication Auteurs : Jarir Saleh, Auteur ; Sungpil Yoon, Auteur ; Kevin Choi, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 105 - 115 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] Continuously Operating Reference Station network [Termes IGN] données GPS [Termes IGN] données localisées des bénévoles [Termes IGN] Etats-Unis [Termes IGN] positionnement par GPS [Termes IGN] qualité des données [Termes IGN] série temporelle [Termes IGN] station de référence Résumé : (Auteur) The CORS network is a volunteer-based network of Global Positioning System reference stations located mainly in the US and its territories. We discuss the most recent comprehensive reprocessing of all GPS data collected via this network since 1996. Daily data for GPS weeks 834 through 1933 were reprocessed leading to epoch 2010.0 coordinates and velocities of 3049 stations aligned to IGS14. The updated realization of the US National Spatial Reference System derived in this work has been in use since late 2019. As a validation of the results, the derived velocity field is compared to several other solutions and to three regional geophysical and geodetic velocity models. These comparisons uncovered unstable stations which move differently than the regional kinematics around them. Once these are ignored, we estimate the horizontal and vertical stability of this updated realization to be better than ∼0.3 and ∼0.6 mm/year, respectively. We use the position residuals and estimated uncertainties from this reprocessing to derive long-term stability measures for all active stations serving longer than 3 years. These measures exposed ∼60 CORS with the poorest long-term stability, which have been consequently excluded from serving as mapping control. Numéro de notice : A2021-320 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2020-0041 Date de publication en ligne : 15/01/2021 En ligne : https://doi.org/10.1515/jag-2020-0041 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97476 [article]

GPS + Galileo + QZSS + BDS tightly combined single-epoch single-frequency RTK positioning / Shaolin Zhu in Survey review, vol 53 n°376 (January 2021)  

Permalink

Sub-daily polar motion from GPS, GLONASS, and Galileo / Radoslaw Zajdel in Journal of geodesy, vol 95 n° 1 (January 2021)  

Permalink

Group diagrams for representing trajectories / Maike Buchin in International journal of geographical information science IJGIS, vol 34 n° 12 (December 2020)  

Permalink

From small sets of GPS trajectories to detailed movement profiles: quantifying personalized trip-dependent movement diversity / Elham Naghizade in International journal of geographical information science IJGIS, vol 34 n° 10 (October 2020)  

Permalink

A graph convolutional network model for evaluating potential congestion spots based on local urban built environments / Kun Qin in Transactions in GIS, Vol 24 n° 5 (October 2020)  

Permalink

Integer-estimable GLONASS FDMA model as applied to Kalman-filter-based short- to long-baseline RTK positioning / Pengyu Hou in GPS solutions, Vol 24 n° 4 (October 2020)  

Permalink

Estimating ocean tide loading displacements with GPS and GLONASS / Bogdan Matviichuk in Solid Earth, vol 11 n° 5 (September - October 2020)  

Permalink

Benefits of combining GPS and GLONASS for measuring ocean tide loading displacement / Majid Abbaszadeh in Journal of geodesy, vol 94 n° 7 (July 2020)  

Permalink

Estimation of tropospheric wet refractivity using tomography method and artificial neural networks in Iranian case study / Mir Reza Ghaffari Razin in GPS solutions, Vol 24 n° 3 (July 2020)  

Permalink

Extracting activity patterns from taxi trajectory data: a two-layer framework using spatio-temporal clustering, Bayesian probability and Monte Carlo simulation / Shuhui Gong in International journal of geographical information science IJGIS, vol 34 n° 6 (June 2020)  

Permalink