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Exploring spatiotemporal clusters based on extended kernel estimation methods / Jay Lee in International journal of geographical information science IJGIS, vol 31 n° 5-6 (May-June 2017)
[article]
Titre : Exploring spatiotemporal clusters based on extended kernel estimation methods Type de document : Article/Communication Auteurs : Jay Lee, Auteur ; Junfang Gong, Auteur ; Shengwen Li, Auteur Année de publication : 2017 Article en page(s) : pp 1154 - 1177 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale
[Termes IGN] analyse spatio-temporelle
[Termes IGN] données spatiotemporelles
[Termes IGN] estimation par noyau
[Termes IGN] exploration de données géographiques
[Termes IGN] groupe
[Termes IGN] implémentation (informatique)
[Termes IGN] infraction
[Termes IGN] Ohio (Etats-Unis)
[Termes IGN] système d'information géographiqueRésumé : (auteur) We examined three different ways to integrate spatial and temporal data in kernel density estimation methods (KDE) to identify space–time clusters of geographic events. Spatial data and time data are typically measured in different units along respective dimensions. Therefore, spatial KDE methods require special extensions when incorporating temporal data to detect spatiotemporal clusters of geographical event. In addition to a real-world data set, we applied the proposed methods to simulated data that were generated through random and normal processes to compare results of different kernel functions. The comparison is based on hit rates and values of a compactness index with considerations of both spatial and temporal attributes of the data. The results show that the spatiotemporal KDE (STKDE) can reach higher hit rates while keeping identified hotspots compact. The implementation of these STKDE methods is tested using the 2012 crime event data in Akron, Ohio, as an example. The results show that STKDE methods reveal new perspectives from the data that go beyond what can be extracted by using the conventional spatial KDE. Numéro de notice : A2017-243 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2017.1287371 En ligne : http://dx.doi.org/10.1080/13658816.2017.1287371 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85179
in International journal of geographical information science IJGIS > vol 31 n° 5-6 (May-June 2017) . - pp 1154 - 1177[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 079-2017031 RAB Revue Centre de documentation En réserve L003 Disponible Inverting Glacial Isostatic Adjustment signal using Bayesian framework and two linearly relaxing rheologies / Lambert Caron in Geophysical journal international, vol 209 n° 2 (May 2017)
[article]
Titre : Inverting Glacial Isostatic Adjustment signal using Bayesian framework and two linearly relaxing rheologies Type de document : Article/Communication Auteurs : Lambert Caron, Auteur ; Laurent Métivier , Auteur ; Marianne Greff-Lefftz, Auteur ; Luce Fleitout, Auteur ; Hélène Rouby , Auteur Année de publication : 2017 Projets : TOSCA / Article en page(s) : pp 1126 - 1147 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] anomalie de pesanteur
[Termes IGN] calotte glaciaire
[Termes IGN] élasticité
[Termes IGN] gravimétrie spatiale
[Termes IGN] manteau terrestre
[Termes IGN] méthode de Monte-Carlo par chaînes de Markov
[Termes IGN] rebond post-glaciaire
[Termes IGN] rhéologieRésumé : (Auteur) Glacial Isostatic Adjustment (GIA) models commonly assume a mantle with a viscoelastic Maxwell rheology and a fixed ice history model. Here, we use a Bayesian Monte Carlo approach with a Markov chain formalism to invert the global GIA signal simultaneously for the mechanical properties of the mantle and the volumes of the ice sheets, using as starting ice models two previously published ice histories. Two stress relaxing rheologies are considered: Burgers and Maxwell linear viscoelasticities. A total of 5720 global palaeo sea level records are used, covering the last 35 kyr. Our goal is not only to seek the model best fitting this data set, but also to determine and display the range of possible solutions with their respective probability of explaining the data. In all cases, our a posteriori probability maps exhibit the classic character of solutions for GIA-determined mantle viscosity with two distinct peaks. What is new in our treatment is the presence of the bi-viscous Burgers rheology and the fact that we invert rheology jointly with ice history, in combination with the greatly expanded palaeo sea level records. The solutions tend to be characterized by an upper-mantle viscosity of around 5 × 1020 Pa s with one preferred lower-mantle viscosities at 3 × 1021 Pa s and the other more than 2 × 1022 Pa s, a rather classical pairing. Best-fitting models depend upon the starting ice history and the stress relaxing law. A first peak (P1) has the highest probability only in the case with a Maxwell rheology and ice history based on ICE-5G, while the second peak (P2) is favoured for ANU-based ice history or Burgers stress relaxation. The latter solution also may satisfy lower-mantle viscosity inferences from long-term geodynamics and gravity gradient anomalies over Laurentia. P2 is also consistent with large Laurentian and Fennoscandian ice-sheet volumes at the Last Glacial Maximum (LGM) and smaller LGM Antarctic ice volume than in either ICE-5G or ANU. Exploration of a bi-viscous linear relaxing rheology in GIA now seems logical due to a new set of requirements to satisfy observations of transient post-seismic flow seen so ubiquitously in space gravimetry and other global geodetic data. Numéro de notice : A2017-402 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggx083 Date de publication en ligne : 27/02/2017 En ligne : https://doi.org/10.1093/gji/ggx083 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86108
in Geophysical journal international > vol 209 n° 2 (May 2017) . - pp 1126 - 1147[article]Kindred spirits : laser ranging to GNSS satellites / Urs Hugentobler in GPS world, vol 28 n° 5 (May 2017)
[article]
Titre : Kindred spirits : laser ranging to GNSS satellites Type de document : Article/Communication Auteurs : Urs Hugentobler, Auteur Année de publication : 2017 Article en page(s) : pp 42 - 48 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] constellation Galileo
[Termes IGN] erreur systématique
[Termes IGN] positionnement par GNSS
[Termes IGN] rétroréflecteur
[Termes IGN] télémétrie laser sur satelliteRésumé : (Auteur) Satellite laser ranging or SLR has been an indispensable independent tool for validating the precise orbits determined for GNSS satellites using microwave pseudorange and carrierphase observations for several decades. SLR has allowed researchers to identify several orbit-modeling issues. Adding albedo radiation pressure and antenna thrust, among other effects, into the GPS orbit model allowed them to eliminate the observed bias between microwave- and SLR-derived orbits. For the first Galileo satellites launched, SLR residuals indicated severe orbit modeling issues caused by the different shape of Galileo satellite bodies compared to those of GPS. In the future, all GNSS satellites will be equipped with laser retroreflectors, a big challenge for researchers concerning tracking scenarios and observation planning to make economic use of the ground equipment. In this article, we will take a brief look at the history of laser ranging to navigation satellites, how that ranging has improved the accuracy of the orbits of those satellites, and what the future portends for this important contribution to space geodesy. Numéro de notice : A2017-293 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85329
in GPS world > vol 28 n° 5 (May 2017) . - pp 42 - 48[article]On the short-term temporal variations of GNSS receiver differential phase biases / Baocheng Zhang in Journal of geodesy, vol 91 n° 5 (May 2017)
[article]
Titre : On the short-term temporal variations of GNSS receiver differential phase biases Type de document : Article/Communication Auteurs : Baocheng Zhang, Auteur ; Peter J.G. Teunissen, Auteur ; Yunbin Yuan, Auteur Année de publication : 2017 Article en page(s) : pp 563 – 572 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] données GNSS
[Termes IGN] erreur de phase
[Termes IGN] erreur systématique
[Termes IGN] positionnement différentiel
[Termes IGN] température au sol
[Termes IGN] teneur totale en électrons
[Termes IGN] trajet multiple
[Termes IGN] variation temporelleRésumé : (auteur) As a first step towards studying the ionosphere with the global navigation satellite system (GNSS), leveling the phase to the code geometry-free observations on an arc-by-arc basis yields the ionospheric observables, interpreted as a combination of slant total electron content along with satellite and receiver differential code biases (DCB). The leveling errors in the ionospheric observables may arise during this procedure, which, according to previous studies by other researchers, are due to the combined effects of the code multipath and the intra-day variability in the receiver DCB. In this paper we further identify the short-term temporal variations of receiver differential phase biases (DPB) as another possible cause of leveling errors. Our investigation starts by the development of a method to epoch-wise estimate between-receiver DPB (BR-DPB) employing (inter-receiver) single-differenced, phase-only GNSS observations collected from a pair of receivers creating a zero or short baseline. The key issue for this method is to get rid of the possible discontinuities in the epoch-wise BR-DPB estimates, occurring when satellite assigned as pivot changes. Our numerical tests, carried out using Global Positioning System (GPS, US GNSS) and BeiDou Navigation Satellite System (BDS, Chinese GNSS) observations sampled every 30 s by a dedicatedly selected set of zero and short baselines, suggest two major findings. First, epoch-wise BR-DPB estimates can exhibit remarkable variability over a rather short period of time (e.g. 6 cm over 3 h), thus significant from a statistical point of view. Second, a dominant factor driving this variability is the changes of ambient temperature, instead of the un-modelled phase multipath. Numéro de notice : A2017-228 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0983-9 En ligne : http://dx.doi.org/10.1007/s00190-016-0983-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85109
in Journal of geodesy > vol 91 n° 5 (May 2017) . - pp 563 – 572[article]Forest classification and impact of BIOMASS resolution on forest area and aboveground biomass estimation / Michael Schlund in International journal of applied Earth observation and geoinformation, vol 56 (April 2017)
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Titre : Forest classification and impact of BIOMASS resolution on forest area and aboveground biomass estimation Type de document : Article/Communication Auteurs : Michael Schlund, Auteur ; Klaus Scipal, Auteur ; Malcolm W.J. Davidson, Auteur Année de publication : 2017 Article en page(s) : pp 65 - 76 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications
[Termes IGN] bande P
[Termes IGN] base de données d'occupation du sol
[Termes IGN] biomasse aérienne
[Termes IGN] biomasse forestière
[Termes IGN] erreur systématique
[Termes IGN] estimation statistique
[Termes IGN] image radar moiréeRésumé : (auteur) The European Space Agency (ESA) is currently implementing the BIOMASS mission as 7th Earth Explorer satellite. BIOMASS will provide for the first time global forest aboveground biomass estimates based on P-band synthetic aperture radar (SAR) imagery. This paper addresses an often overlooked element of the data processing chain required to ensure reliable and accurate forest biomass estimates: accurate identification of forest areas ahead of the inversion of radar data into forest biomass estimates. The use of the P-band data from BIOMASS itself for the classification into forest and non-forest land cover types is assessed in this paper. For airborne data in tropical, hemi-boreal and boreal forests we demonstrate that classification accuracies from 90 up to 97% can be achieved using radar backscatter and phase information. However, spaceborne data will have a lower resolution and higher noise level compared to airborne data and a higher probability of mixed pixels containing multiple land cover types. Therefore, airborne data was reduced to 50 m, 100 m and 200 m resolution. The analysis revealed that about 50–60% of the area within the resolution level must be covered by forest to classify a pixel with higher probability as forest compared to non-forest. This results in forest omission and commission leading to similar forest area estimation over all resolutions. However, the forest omission resulted in a biased underestimated biomass, which was not equaled by the forest commission. The results underline the necessity of a highly accurate pre-classification of SAR data for an accurate unbiased aboveground biomass estimation. Numéro de notice : A2017-370 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jag.2016.12.001 En ligne : https://doi.org/10.1016/j.jag.2016.12.001 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85789
in International journal of applied Earth observation and geoinformation > vol 56 (April 2017) . - pp 65 - 76[article]Hyperspectral band selection from statistical wavelet models / Siwei Feng in IEEE Transactions on geoscience and remote sensing, vol 55 n° 4 (April 2017)PermalinkIntegrating cellular automata and Markov techniques to generate urban development potential surface : a study on Kolkata agglomeration / Biswajit Mondal in Geocarto international, vol 32 n° 4 (April 2017)PermalinkIntegrating uncertainty propagation in GNSS radio occultation retrieval: From bending angle to dry-air atmospheric profiles / Jakob Schwarz in Earth and space science, vol 4 n° 4 (April 2017)PermalinkMinimizing construction emissions using Building Information Modeling and Decision-Making techniques / Mohamed Marzouk in International journal of 3-D information modeling, vol 6 n° 2 (April-June 2017)PermalinkPerformance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions / O. E. Abe in Journal of geodesy, vol 91 n° 4 (April 2017)PermalinkBias compensation for rational function model based on total least squares / Anzhu Yu in Photogrammetric record, vol 32 n° 157 (March - May 2017)PermalinkDetermining the appropriate timing of the next forest inventory: incorporating forest owner risk preferences and the uncertainty of forest data quality / Kyle J. Eyvindson in Annals of Forest Science, vol 74 n° 1 (March 2017)PermalinkEstimation and analysis of Galileo differential code biases / Min Li in Journal of geodesy, vol 91 n° 3 (March 2017)PermalinkImage-based target detection and radial velocity estimation methods for multichannel SAR-GMTI / Kei Suwa in IEEE Transactions on geoscience and remote sensing, vol 55 n° 3 (March 2017)PermalinkMapping forest attributes using data from stereophotogrammetry of aerial images and field data from the national forest inventory / Jonas Bohlin in Silva fennica, vol 51 n° 2 (2017)Permalink