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Spatiotemporal accuracy evaluation and errors analysis of global VTEC maps using a simulation technique / Jian Lin in GPS solutions, vol 27 n° 1 (January 2023)  

Public [article]  inGPS solutions > vol 27 n° 1 (January 2023) . - n° 6 Titre : Spatiotemporal accuracy evaluation and errors analysis of global VTEC maps using a simulation technique Type de document : Article/Communication Auteurs : Jian Lin, Auteur ; Xinxing Li, Auteur ; Shenfeng Gu, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 6 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données GPS [Termes IGN] harmonique sphérique [Termes IGN] modèle cartographique [Termes IGN] modèle ionosphérique [Termes IGN] phase [Termes IGN] rayonnement solaire [Termes IGN] simulation [Termes IGN] station GPS [Termes IGN] teneur verticale totale en électrons Résumé : (auteur) The computation of vertical total electron content (VTEC) maps has become an important issue gradually for the international GNSS service. Given the current literature reports, little research is involved in the quantitative analysis of each error of the VTEC map and the spatiotemporal characteristic of global VTEC accuracy. Based on the single layer model and sphere harmonic function, we propose an approach using simulated GPS data to comprehensively verify the accuracy of the VTEC map. The spatiotemporal characteristic of global VTEC accuracy and the errors induced by different processing steps, i.e., carrier phase to code leveling, mapping function (MF), DCB estimation and coefficient fitting, are analyzed and discussed in detail. In addition, the effect of solar activity on the accuracy of the global VTEC map, MF and DCB estimation has been discussed. The results suggest: First, it is found that the MF error at sunrise is more significant than that at sunset, and this important characteristic can be proven based on the analysis of theory and ionospheric radio occultation and VTEC measurements; second, the MF is the most significant error source in the VTEC processing for regions with dense and homogeneous distributed GPS stations, e.g., North America and Europe. The VTEC accuracy in these regions can be improved by 100% with the satellite elevation cutoff angle increasing from 12° to 30°; finally, compared with the global VTEC accuracy using 350 GPS stations observations, the accuracy is improved by 306% based on the double GPS stations with even distribution. Numéro de notice : A2023-002 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-022-01343-y Date de publication en ligne : 13/10/2022 En ligne : https://doi.org/10.1007/s10291-022-01343-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101871 [article]

Estimation of swell height using spaceborne GNSS-R data from eight CYGNSS satellites / Yanli Zheng in Remote sensing, vol 14 n° 18 (September-2 2022)  

Public [article]  inRemote sensing > vol 14 n° 18 (September-2 2022) . - n° 4640 Titre : Estimation of swell height using spaceborne GNSS-R data from eight CYGNSS satellites Type de document : Article/Communication Auteurs : Yanli Zheng, Auteur ; Fu Zheng, Auteur ; Cheng Yang, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 4640 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données GLONASS [Termes IGN] données GPS [Termes IGN] double différence [Termes IGN] latitude [Termes IGN] positionnement ponctuel précis [Termes IGN] positionnement statique [Termes IGN] retard troposphérique zénithal [Termes IGN] temps de convergence Résumé : (auteur) The orbital inclination angle of the GLONASS constellation is about 10° larger than that of GPS, Galileo, and BDS. Theoretically, the higher orbital inclination angle could provide better observation geometry in high latitude regions. A wealth of research has investigated the positioning accuracy of GLONASS and its impact on multi-GNSS, but rarely considered the contribution of the GLONASS constellation’s large orbit inclination angle. The performance of GLONASS in different latitude regions is evaluated in both stand-alone mode and integration with GPS in this paper. The performance of GPS is also presented for comparison. Three international GNSS service (IGS) networks located in high, middle, and low latitudes are selected for the current study. Multi-GNSS data between January 2021 and June 2021 are used for the assessment. The data quality check shows that the GLONASS data integrity is significantly lower than that of GPS. The constellation visibility analysis indicates that GLONASS has a much better elevation distribution than GPS in high latitude regions. Both daily double-difference network solutions and daily static Precise Point Positioning (PPP) solutions are evaluated. The statistical analysis of coordinate estimates indicates that, in high latitude regions, GLONASS has a comparable or even better accuracy than that of GPS, and GPS+GLONASS presents the best estimate accuracy; in middle latitude regions, GPS stand-alone constellation provides the best positioning accuracy; in low latitude regions, GLONASS offers the worst accuracy, but the positioning accuracy of GPS+GLONASS is better than that of GPS. The tropospheric estimates of GLONASS do not present a resemblance regional advantage as coordinate estimates, which is worse than that of GPS in all three networks. The PPP processing with combined GPS and GLONASS observations reduces the convergence time and improves the accuracy of tropospheric estimates in all three networks. Numéro de notice : A2022-770 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3390/rs14184640 Date de publication en ligne : 16/09/2022 En ligne : https://doi.org/10.3390/rs14184640 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101796 [article]

An improved vertical correction method for the inter-comparison and inter-validation of Integrated Water Vapour measurements [under review] / Olivier Bock in Atmospheric measurement techniques, vol 15 n° 19 ([01/04/2022])  

Public [article]  inAtmospheric measurement techniques > vol 15 n° 19 [01/04/2022] . - pp 5643 - 5665 Titre : An improved vertical correction method for the inter-comparison and inter-validation of Integrated Water Vapour measurements [under review] Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Pierre Bosser , Auteur ; Carl Mears, Auteur Année de publication : 2022 Projets : VEGAN / Bock, Olivier Article en page(s) : pp 5643 - 5665 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-15-5643-2022 Date de publication en ligne : 21/04/2022 En ligne : https://doi.org/10.5194/amt-15-5643-2022 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]

Application of machine learning to predict transport modes from GPS, accelerometer, and heart rate data / Santosh Giri in International Journal of Health Geographics, vol 21 (2022)  

Public [article]  inInternational Journal of Health Geographics > vol 21 (2022) . - n° 19 Titre : Application of machine learning to predict transport modes from GPS, accelerometer, and heart rate data Type de document : Article/Communication Auteurs : Santosh Giri, Auteur ; Ruben Brondeel, Auteur ; Tarik El Aarbaoui, Auteur ; Basile Chaix, Auteur Année de publication : 2022 Article en page(s) : n° 19 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes IGN] accéléromètre [Termes IGN] bicyclette [Termes IGN] données GPS [Termes IGN] données médicales [Termes IGN] Ile-de-France [Termes IGN] transport public Résumé : (auteur) Background : There has been an increased focus on active transport, but the measurement of active transport is still difficult and error-prone. Sensor data have been used to predict active transport. While heart rate data have very rarely been considered before, this study used random forests (RF) to predict transport modes using Global Positioning System (GPS), accelerometer, and heart rate data and paid attention to methodological issues related to the prediction strategy and post-processing. Methods : The RECORD MultiSensor study collected GPS, accelerometer, and heart rate data over seven days from 126 participants living in the Ile-de-France region. RF models were built to predict transport modes for every minute (ground truth information on modes is from a GPS-based mobility survey), splitting observations between a Training dataset and a Test dataset at the participant level instead at the minute level. Moreover, several window sizes were tested for the post-processing moving average of the predicted transport mode. Results : The minute-level prediction rate of being on trips vs. at a visited location was 90%. Final prediction rates of transport modes ranged from 65% for public transport to 95% for biking. Using minute-level observations from the same participants in the Training and Test sets (as RF spontaneously does) upwardly biases prediction rates. The inclusion of heart rate data improved prediction rates only for biking. A 3 to 5-min bandwidth moving average was optimum for a posteriori homogenization. Conclusion : Heart rate only very slightly contributed to better predictions for specific transport modes. Moreover, our study shows that Training and Test sets must be carefully defined in RF models and that post-processing with carefully chosen moving average windows can improve predictions. Numéro de notice : A2022-077 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1186/s12942-022-00319-y Date de publication en ligne : 16/11/2022 En ligne : https://doi.org/10.1186/s12942-022-00319-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102445 [article]

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

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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)  

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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)  

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

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

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

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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)  

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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)  

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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)  

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

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