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Estimation and analysis of GPS inter-fequency clock biases from long-term triple-frequency observations / Fan Zhang in GPS solutions, vol 25 n° 4 (October 2021)  

Public [article]  inGPS solutions > vol 25 n° 4 (October 2021) . - n° 126 Titre : Estimation and analysis of GPS inter-fequency clock biases from long-term triple-frequency observations Type de document : Article/Communication Auteurs : Fan Zhang, Auteur ; Hongzhou Chai, Auteur ; Linyang Li, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 126 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] décalage d'horloge [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] fréquence multiple [Termes IGN] phase GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] station GNSS [Termes IGN] triple différence [Termes IGN] variation temporelle Résumé : (auteur) Usually, the difference between the satellite clocks computed with L1/L2 and clocks computed with L1/L5 is defined as inter-frequency clock bias (IFCB). It is critical to correct its L5 time-variant portion in the GNSS triple-frequency precise positioning. Using two years of observations from more than 100 stations worldwide, we use the epoch-differenced method to estimate IFCB for all available 12 GPS BLOCK-IIF satellites, and analyze its short-term and long-term variations. The experimental results indicate that the IFCB variations are clearly consistent for two satellites located in the same orbital plane, which perhaps means that the variations of IFCB are dependent on the orbital plane. We found that the IFCB of each Block-IIF satellite shows repetition characteristics over two years. The annual repetition cycle of 352 days of IFCB is consistent with the GPS year 351.4 days may originate from the rotation of satellites around the earth. GPS triple-frequency uncombined PPP is carried out using 9 globally distributed MGEX stations from June 1 to 30, 2018. The experimental results indicate that compared to the PPP solutions without IFCB corrections, GPS triple-frequency PPP can achieve an accuracy of 2.2, 3.8 and 11.4 mm in the north, east, and up components after correcting IFCB, which is an accuracy increase in 31.3%, 17.4%, and 13.0%, respectively. The average RMS of the phase posteriori residuals for each frequency is also reduced significantly, especially 79.1% for L5 frequency. Numéro de notice : A2021-565 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-021-01161-8 date de publication en ligne : 10/07/2021 En ligne : https://doi.org/10.1007/s10291-021-01161-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98134 [article]

Detection of aspen in conifer-dominated boreal forests with seasonal multispectral drone image point clouds / Alwin A. Hardenbol in Silva fennica, vol 55 n° 4 (September 2021)  

Public [article]  inSilva fennica > vol 55 n° 4 (September 2021) . - n° 10515 Titre : Detection of aspen in conifer-dominated boreal forests with seasonal multispectral drone image point clouds Type de document : Article/Communication Auteurs : Alwin A. Hardenbol, Auteur ; Anton Kuzmin, Auteur ; Lauri Korhonen, Auteur ; Pasi Korpelainen, Auteur ; Timo Kumpula, Auteur ; Matti Maltamo, Auteur ; Jari Kouki, Auteur Année de publication : 2021 Article en page(s) : n° 10515 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] aire protégée [Termes IGN] analyse discriminante [Termes IGN] Betula (genre) [Termes IGN] détection d'arbres [Termes IGN] forêt boréale [Termes IGN] image captée par drone [Termes IGN] image multibande [Termes IGN] orthoimage couleur [Termes IGN] peuplement mélangé [Termes IGN] Picea abies [Termes IGN] Pinus sylvestris [Termes IGN] Populus tremula [Termes IGN] semis de points [Termes IGN] variation saisonnière Résumé : (auteur) Current remote sensing methods can provide detailed tree species classification in boreal forests. However, classification studies have so far focused on the dominant tree species, with few studies on less frequent but ecologically important species. We aimed to separate European aspen (Populus tremula L.), a biodiversity-supporting tree species, from the more common species in European boreal forests (Pinus sylvestris L., Picea abies [L.] Karst., Betula spp.). Using multispectral drone images collected on five dates throughout one thermal growing season (May–September), we tested the optimal season for the acquisition of mono-temporal data. These images were collected from a mature, unmanaged forest. After conversion into photogrammetric point clouds, we segmented crowns manually and automatically and classified the species by linear discriminant analysis. The highest overall classification accuracy (95%) for the four species as well as the highest classification accuracy for aspen specifically (user’s accuracy of 97% and a producer’s accuracy of 96%) were obtained at the beginning of the thermal growing season (13 May) by manual segmentation. On 13 May, aspen had no leaves yet, unlike birches. In contrast, the lowest classification accuracy was achieved on 27 September during the autumn senescence period. This is potentially caused by high intraspecific variation in aspen autumn coloration but may also be related to our date of acquisition. Our findings indicate that multispectral drone images collected in spring can be used to locate and classify less frequent tree species highly accurately. The temporal variation in leaf and canopy appearance can alter the detection accuracy considerably. Numéro de notice : A2021-735 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.14214/sf.10515 date de publication en ligne : 14/07/2021 En ligne : https://doi.org/10.14214/sf.10515 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98691 [article]

Monitoring forest disturbance using time-series MODIS NDVI in Michoacán, Mexico / Yao Gao in Geocarto international, Vol 36 n° 15 ([10/08/2021])  

Public [article]  inGeocarto international > Vol 36 n° 15 [10/08/2021] . - pp 1768 - 1784 Titre : Monitoring forest disturbance using time-series MODIS NDVI in Michoacán, Mexico Type de document : Article/Communication Auteurs : Yao Gao, Auteur ; Alexander Quevedo, Auteur ; Zoltan Szantoi, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 1768 - 1784 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] détection de changement [Termes IGN] fonction harmonique [Termes IGN] image Terra-MODIS [Termes IGN] inventaire forestier étranger (données) [Termes IGN] Mexique [Termes IGN] Normalized Difference Vegetation Index [Termes IGN] série temporelle [Termes IGN] surveillance forestière [Termes IGN] variation saisonnière Résumé : (auteur) MODIS-based NDVI time series (2000–2016) was applied to monitor sub-annual forest disturbance in the Mexican state of Michoacán, with an algorithm that decomposes the time-series data into a harmonic function and a trend. To detect change, a moving sum of residuals between the observed and predicted NDVI values was compared with that from the reference period. Magnitude of change was computed by subtracting the predicted NDVI from the observed one. By comparing the detected changes with reference data through visual interpretation, a threshold of |0.05| was established as the magnitude of change for forest disturbance detection. The method detected more forest gain than loss for 2013–2016, a result which is supported by recent findings from the national forest inventory. Forest loss decreases yearly for 2013–2016, and forest gain peaks at 2014 and 2015. We verified the findings with data from the global forest cover change project. Numéro de notice : A2021-580 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106049.2019.1661032 date de publication en ligne : 09/09/2019 En ligne : https://doi.org/10.1080/10106049.2019.1661032 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98185 [article]

Comparison of polar ionospheric behavior at Arctic and Antarctic regions for improved satellite-based positioning / Arun Kumar Singh in Journal of applied geodesy, vol 15 n° 3 (July 2021)  

Public [article]  inJournal of applied geodesy > vol 15 n° 3 (July 2021) . - pp 269 - 277 Titre : Comparison of polar ionospheric behavior at Arctic and Antarctic regions for improved satellite-based positioning Type de document : Article/Communication Auteurs : Arun Kumar Singh, Auteur Année de publication : 2021 Article en page(s) : pp 269 - 277 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] amplitude [Termes IGN] Antarctique [Termes IGN] Arctique [Termes IGN] champ géomagnétique [Termes IGN] ionosphère [Termes IGN] magnétosphère [Termes IGN] phase [Termes IGN] pôle [Termes IGN] positionnement par GNSS [Termes IGN] retard ionosphèrique [Termes IGN] scintillation [Termes IGN] teneur totale en électrons [Termes IGN] variation temporelle Résumé : (Auteur) In this paper, we investigate the hemispheric symmetric and asymmetric characteristics of ionospheric total electron content (TEC) and its dependency on the interplanetary magnetic field (IMF) in the northern and southern polar ionosphere. The changes in amplitude and phase scintillation are also probed through Global Ionospheric Scintillation and TEC monitoring (GISTM) systems recordings at North pole [Himadri station; Geographic 78°55′ N, 11°56′ E] and South pole [Maitri station; Geographic 70°46′ S 11°44′ E]. Observations show the range of %TEC variability being relatively more over Antarctic region (−40 % to 60 %) than Arctic region (−25 % to 25 %), corroborating the role of the dominant solar photoionization production process. Our analysis confirms that TEC variation at polar latitudes is a function of magnetosphere-ionosphere coupling, depending on interplanetary magnetic field (IMF) orientation and magnitude in the X ( Bx), Y ( By), and Z ( Bz) plane. Visible enhancement in TEC is noticed in the northern polar latitude when Bx6nT and Bz>0 whereas the southern polar latitude perceives TEC enhancements with Bx>0, −6nT Numéro de notice : A2021-469 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2021-0033 date de publication en ligne : 22/06/2021 En ligne : https://doi.org/10.1515/jag-2021-0033 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98107 [article]

Pedestrian fowl prediction in open public places using graph convolutional network / Menghang Liu in ISPRS International journal of geo-information, vol 10 n° 7 (July 2021)  

Public [article]  inISPRS International journal of geo-information > vol 10 n° 7 (July 2021) . - n° 455 Titre : Pedestrian fowl prediction in open public places using graph convolutional network Type de document : Article/Communication Auteurs : Menghang Liu, Auteur ; Luning Li, Auteur ; Qiang Li, Auteur Année de publication : 2021 Article en page(s) : n° 455 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes IGN] espace public [Termes IGN] flux [Termes IGN] modèle de simulation [Termes IGN] navigation pédestre [Termes IGN] planification urbaine [Termes IGN] réseau neuronal de graphes [Termes IGN] Shenzhen [Termes IGN] variation temporelle Résumé : (auteur) Open public places, such as pedestrian streets, parks, and squares, are vulnerable when the pedestrians thronged into the sidewalks. The crowd count changes dynamically over time with various external factors, such as surroundings, weekends, and peak hours, so it is essential to predict the accurate and timely crowd count. To address this issue, this study introduces graph convolutional network (GCN), a network-based model, to predict the crowd flow in a walking street. Compared with other grid-based methods, the model is capable of directly processing road network graphs. Experiments show the GCN model and its extension STGCN consistently and significantly outperform other five baseline models, namely HA, ARIMA, SVM, CNN and LSTM, in terms of RMSE, MAE and R2. Considering the computation efficiency, the standard GCN model was selected to predict the crowd. The results showed that the model obtains superior performances with higher prediction precision on weekends and peak hours, of which R2 are above 0.9, indicating the GCN model can capture the pedestrian features in the road network effectively, especially during the periods with massive crowds. The results will provide practical references for city managers to alleviate road congestion and help pedestrians make smarter planning and save travel time. Numéro de notice : A2021-550 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.3390/ijgi10070455 date de publication en ligne : 02/07/2021 En ligne : https://doi.org/10.3390/ijgi10070455 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98073 [article]

On the relationship between normalized difference vegetation index and land surface temperature: MODIS-based analysis in a semi-arid to arid environment / Salahuddin M. Jaber in Geocarto international, vol 36 n° 10 ([01/06/2021])  

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Reference evapotranspiration (ETo) methods implemented as ArcMap models with remote-sensed and ground-based inputs, examined along with MODIS ET, for Peloponnese, Greece / Stavroula Dimitriadou in ISPRS International journal of geo-information, vol 10 n° 6 (June 2021)  

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Assessing forest phenology: A multi-scale comparison of near-surface (UAV, spectral reflectance sensor, PhenoCam) and satellite (MODIS, Sentinel-2) remote sensing / Shangharsha Thapa in Remote sensing, vol 13 n° 8 (April-2 2021)  

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Assessment of degree-2 order-1 gravitational changes from GRACE and GRACE Follow-on, Earth rotation, satellite laser ranging, and models / Jianli Chen in Journal of geodesy, vol 95 n° 4 (April 2021)  

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Geovisualization of COVID-19: State of the art and opportunities / Yu Lan in Cartographica, vol 56 n° 1 (Spring 2021)  

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Precipitable water vapor fusion based on a generalized regression neural network / Bao Zhang in Journal of geodesy, vol 95 n° 4 (April 2021)  

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Urban heat island formation in greater Cairo: Spatio-temporal analysis of daytime and nighttime land surface temperatures along the urban–rural gradient / Darshana Athukorala in Remote sensing, vol 13 n° 7 (April 2021)  

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Terrestrial laser scanning intensity captures diurnal variation in leaf water potential / S. Junttila in Remote sensing of environment, Vol 255 (March 2021)  

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Is the seasonal variation in frost resistance and plant performance in four oak species affected by changing temperatures? / Maggie Preißer in Forests, vol 12 n° 3 (March 2021)  

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Radar measurements of snow depth over sea ice on an unmanned aerial vehicle / Adrian Eng-Choon Tan in IEEE Transactions on geoscience and remote sensing, Vol 59 n° 3 (March 2021)  

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