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Impact of travel time uncertainties on modeling of spatial accessibility: a comparison of street data sources / Yan Lin in Cartography and Geographic Information Science, vol 48 n° 6 (October 2021)  

Public [article]  inCartography and Geographic Information Science > vol 48 n° 6 (October 2021) . - pp 471 - 490 Titre : Impact of travel time uncertainties on modeling of spatial accessibility: a comparison of street data sources Type de document : Article/Communication Auteurs : Yan Lin, Auteur ; Christopher Lippitt, Auteur ; Daniel Beene, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 471 - 490 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes IGN] accessibilité [Termes IGN] analyse de sensibilité [Termes IGN] ArcMap [Termes IGN] données localisées des bénévoles [Termes IGN] durée de trajet [Termes IGN] Google Maps [Termes IGN] incertitude des données [Termes IGN] indexation spatiale [Termes IGN] navigation automobile [Termes IGN] Nouveau-Mexique (Etats-Unis) [Termes IGN] OpenStreetMap [Termes IGN] plan de déplacement urbain [Termes IGN] réseau routier [Termes IGN] système d'information géographique [Termes IGN] transport public Résumé : (auteur) GIS-based spatial access measures have been used extensively to monitor social equity and to help develop policy. However, inherent uncertainties in the road datasets used in spatial access estimates remain largely underreported. These uncertainties might result in unrecognized biases within visualization products and decision-making outcomes that strive to improve social equity based on seemingly egalitarian accessibility metrics. To better understand and address these uncertainties, we evaluated variations in travel impedance for car and bus transportation using proprietary, volunteer-information-based, and free (non-volunteer-information-based) street networks. We then interpreted the measured variations through the lens of street data uncertainty and its propagation in a common E2SFCA model of spatial accessibility. Results indicated that travel impedance disagreement propagates through the modeling process to effect agreement of spatial access index (SPAI) estimates among different street sources, with larger uncertainties observed for bus travel than car travel. Higher impedance coefficients (β), a model parameter, reduced the impact of street-source variations on estimates. Less urbanized regions were found to experience higher street-source variations when compared with the core-metropolitan area. We also demonstrated that a relative spatial access measure – the spatial access ratio (SPAR) – reduced uncertainties introduced by the choice of street datasets. Careful selection of reliable street sources and model parameters (e.g. higher β), as well as consideration of the potential for bias, particularly for less urbanized areas and areas reliant on public transportation, is warranted when leveraging SPAI to inform policy. When reliable/accurate road network data are not accessible or data quality information is not available, the SPAR is a suitable alternative or supplement to SPAI for visualization and analyses. Numéro de notice : A2021-712 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/15230406.2021.1960609 Date de publication en ligne : 01/09/2021 En ligne : https://doi.org/10.1080/15230406.2021.1960609 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98617 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
032-2021061	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Fusing tree‐ring and forest inventory data to infer influences on tree growth / Margaret E.K. Evans in Ecosphere, vol 8 n° 7 (July 2017)  

Public [article]  inEcosphere > vol 8 n° 7 (July 2017) Titre : Fusing tree‐ring and forest inventory data to infer influences on tree growth Type de document : Article/Communication Auteurs : Margaret E.K. Evans, Auteur ; Donald A. Falk, Auteur ; et al., Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] changement climatique [Termes IGN] classification bayesienne [Termes IGN] croissance des arbres [Termes IGN] dendrochronologie [Termes IGN] inférence statistique [Termes IGN] inventaire forestier étranger (données) [Termes IGN] modèle statistique [Termes IGN] montagne [Termes IGN] Nouveau-Mexique (Etats-Unis) [Termes IGN] régression multiple [Vedettes matières IGN] Végétation et changement climatique Résumé : (auteur) Better understanding and prediction of tree growth is important because of the many ecosystem services provided by forests and the uncertainty surrounding how forests will respond to anthropogenic climate change. With the ultimate goal of improving models of forest dynamics, here we construct a statistical model that combines complementary data sources, tree‐ring and forest inventory data. A Bayesian hierarchical model was used to gain inference on the effects of many factors on tree growth—individual tree size, climate, biophysical conditions, stand‐level competitive environment, tree‐level canopy status, and forest management treatments—using both diameter at breast height (dbh) and tree‐ring data. The model consists of two multiple regression models, one each for the two data sources, linked via a constant of proportionality between coefficients that are found in parallel in the two regressions. This model was applied to a data set of ~130 increment cores and ~500 repeat measurements of dbh at a single site in the Jemez Mountains of north‐central New Mexico, USA. The tree‐ring data serve as the only source of information on how annual growth responds to climate variation, whereas both data types inform non‐climatic effects on growth. Inferences from the model included positive effects on growth of seasonal precipitation, wetness index, and height ratio, and negative effects of dbh, seasonal temperature, southerly aspect and radiation, and plot basal area. Climatic effects inferred by the model were confirmed by a dendroclimatic analysis. Combining the two data sources substantially reduced uncertainty about non‐climate fixed effects on radial increments. This demonstrates that forest inventory data measured on many trees, combined with tree‐ring data developed for a small number of trees, can be used to quantify and parse multiple influences on absolute tree growth. We highlight the kinds of research questions that can be addressed by combining the high‐resolution information on climate effects contained in tree rings with the rich tree‐ and stand‐level information found in forest inventories, including projection of tree growth under future climate scenarios, carbon accounting, and investigation of management actions aimed at increasing forest resilience. Numéro de notice : A2017-907 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1002/ecs2.1889 Date de publication en ligne : 24/07/2017 En ligne : https://doi.org/10.1002/ecs2.1889 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93405 [article]

Evaluating the use of GPS heights in water conservation applications / Ahmed F. Elaksher in Survey review, vol 48 n° 348 (May 2016)  

Public [article]  inSurvey review > vol 48 n° 348 (May 2016) . - pp 195 - 201 Titre : Evaluating the use of GPS heights in water conservation applications Type de document : Article/Communication Auteurs : Ahmed F. Elaksher, Auteur ; A. Fernald, Auteur ; F. Kapoko, Auteur Année de publication : 2016 Article en page(s) : pp 195 - 201 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie [Termes IGN] altitude orthométrique [Termes IGN] analyse comparative [Termes IGN] GPS en mode statique [Termes IGN] hauteur ellipsoïdale [Termes IGN] niveau de l'eau [Termes IGN] nivellement indirect [Termes IGN] Nouveau-Mexique (Etats-Unis) [Termes IGN] positionnement par GPS [Termes IGN] positionnement statique rapide [Termes IGN] récepteur GPS [Termes IGN] station de contrôle [Termes IGN] station de référence Résumé : (auteur) Accurate water level elevations are imperative for water resource management. This paper presents the outcomes of a research study using GPS in measuring water level heights. The authors observed the water elevations of several wells, United States Geological Survey (USGS) gauges and acequia points at three different locations in North–Central New Mexico, USA. Different rapid static and static observation sessions were collected independently and adjusted using the nearby reference control stations. The authors used two different sets of receivers: four Topcon Hiper Lite+ and two Leica GPS1200 The authors were able to examine several network configurations with different continuously operating reference station (CORS) stations. Our findings were analogous to empirically expected errors and showed insignificant differences among the heights obtained from rapid static and static sessions at a 95% confidence level. The authors also compared the results with National Geodetic Survey online positioning users service (NGS OPUS) solutions and confirmed the accuracy of our measurements. As independent measurement technique, we measured the height differences among several of these points with conventional levelling surveys. Our GPS measurements provided small disagreements with height differences obtained with the terrestrial surveys, after the GPS heights were reduced to their orthometric correspondences. Based on these findings, current rapid static GPS positioning methodologies are capable of providing equivalent accuracies as those obtained by static GPS and ground surveying techniques. Numéro de notice : A2016-274 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000021 En ligne : http://doi.org/10.1179/1752270615Y.0000000021 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80829 [article]

Support vector machines for recognition of semi-arid vegetation types using MISR multi-angle imagery / L. Su in Remote sensing of environment, vol 107 n° 1-2 (15 March 2007)  

Public [article]  inRemote sensing of environment > vol 107 n° 1-2 (15 March 2007) . - pp 299 - 311 Titre : Support vector machines for recognition of semi-arid vegetation types using MISR multi-angle imagery Type de document : Article/Communication Auteurs : L. Su, Auteur ; M. Chopping, Auteur ; A. Rango, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 299 - 311 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] carte de la végétation [Termes IGN] classification par séparateurs à vaste marge [Termes IGN] désert [Termes IGN] image Terra-MISR [Termes IGN] Nouveau-Mexique (Etats-Unis) [Termes IGN] prairie [Termes IGN] zone aride [Termes IGN] zone semi-aride Résumé : (Auteur) Accurately mapping community types is one of the main challenges for monitoring arid and semi-arid grasslands with remote sensing. The multi-angle approach has been proven useful for mapping vegetation types in desert grassland. The Multi-angle Imaging Spectro-Radiometer (MISR) provides 4 spectral bands and 9 angular reflectance. In this study, 44 classification experiments have been implemented to find the optimal combination of MISR multi-angular data to mine the information carried by MISR data as effectively as possible. These experiments show the following findings: 1) The combination of MISR's 4 spectral bands at nadir and red and near infrared bands in the C, B, and A cameras observing off-nadir can obtain the best vegetation type differentiation at the community level in New Mexico desert grasslands. 2) The k parameter at red band of Modified–Rahman–Pinty–Verstraete (MRPV) model and the structural scattering index (SSI) can bring useful additional information to land cover classification. The information carried by these two parameters, however, is less than that carried by surface anisotropy patterns described by the MRPV model and a linear semi-empirical kernel-driven bidirectional reflectance distribution function model, the RossThin–LiSparseMODIS (RTnLS) model. These experiments prove that: 1) multi-angular reflectance raise overall classification accuracy from 45.8% for nadir-only reflectance to 60.9%. 2) With surface anisotropy patterns derived from MRPV and RTnLS, an overall accuracy of 68.1% can be obtained when maximum likelihood algorithms are used. 3) Support Vector Machine (SVM) algorithms can raise the classification accuracy to 76.7%. This research shows that multi-angular reflectance, surface anisotropy patterns and SVM algorithms can improve desert vegetation type differentiation importantly. Copyright Elsevier Numéro de notice : A2007-056 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2006.05.023 En ligne : https://doi.org/10.1016/j.rse.2006.05.023 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28421 [article]

ICESat altimetry data product verification at White Sands Space Harbor / L.A. Magruder in IEEE Transactions on geoscience and remote sensing, vol 45 n° 1 (January 2007)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 45 n° 1 (January 2007) . - pp 147 - 155 Titre : ICESat altimetry data product verification at White Sands Space Harbor Type de document : Article/Communication Auteurs : L.A. Magruder, Auteur ; C.E. Webb, Auteur ; T.J. Urban, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 147 - 155 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] altimétrie satellitaire par radar [Termes IGN] contrôle altimétrique [Termes IGN] détection du signal [Termes IGN] données altimétriques [Termes IGN] données ICEsat [Termes IGN] ICEsat [Termes IGN] Nouveau-Mexique (Etats-Unis) [Termes IGN] signal laser [Vedettes matières IGN] Altimétrie Résumé : (Auteur) Three unique techniques have been developed to validate the Ice, Cloud, and Land Elevation Satellite (ICESat) mission altimetry data product and implemented at White Sands Space Harbor (WSSH) in New Mexico. One specific technique at WSSH utilizes zenith-pointed sensors to detect the laser on the surface and enable geolocation determination of the altimeter footprint that is independent of the data product generation. The system of detectors also registers the laser light time of arrival, which is related to the data product time tag. Several overflights of the WSSH have validated these time tags to less than 3+ 1 us. The ground-based detector system also verified the laser illuminated spot geolocation to 10.6 m (3.5 arcsec) + 4.5 m on one occasion, which is consistent with the requirement of 3.5 m (1ó). A third technique using corner cube retroreflector signatures in the altimeter echo waveforms was also shown to provide an assessment of the laser spot geolocation. Although the accuracy of this technique is not equal to the other methodologies, it does offer position determination for comparison to the spacecraft altimetry data product. In addition, elevation verifications were made using the comparison of the ICESat elevation products at WSSH to those acquired with an airborne light detection and ranging. The elevation comparisons show an agreement to within + 34 cm (+ 6.7 cm under best conditions) which indicate no significant errors associated with the pointing knowledge of the altimeter. Copyright IEEE Numéro de notice : A2007-077 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2006.885070 En ligne : https://doi.org/10.1109/TGRS.2006.885070 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28442 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
065-07011	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Predicting riparian evapotranspiration from MODIS vegetation indices and meteorological data / P. Nagler in Remote sensing of environment, vol 94 n° 1 (15/01/2005)  

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Simultaneous block triangulation of the OEEPE SPOT data set / Trifid corporation (1989)

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Selecting the spatial resolution of satellite sensors required for global monitoring of land transformations / J.R.G. Townshend in International Journal of Remote Sensing IJRS, vol 9 n° 2 (February 1988)  

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Classification of geomorphic features and landscape stability in northwestern New Mexico using simulated Spot imagery / K.F. Connors in Remote sensing of environment, vol 22 n° 2 (01/07/1987)  

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Reflectance-based and radiance-based methods for the in-flight absolute calibration of multispectral sensors / P.N. Slater in Remote sensing of environment, vol 22 n° 1 (01/06/1987)  

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Mapping the sun dagger / S. Curry (01/01/1987)

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