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Vectorial algebra algorithms for calculating terrain parameters from DEMs and solar radiation modelling in mountainous terrain / J.G. Corripio in International journal of geographical information science IJGIS, vol 17 n° 1 (february 2003)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 17 n° 1 (february 2003) . - pp 1 - 23 Titre : Vectorial algebra algorithms for calculating terrain parameters from DEMs and solar radiation modelling in mountainous terrain Type de document : Article/Communication Auteurs : J.G. Corripio, Auteur Année de publication : 2003 Article en page(s) : pp 1 - 23 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique [Termes IGN] algèbre [Termes IGN] éclairement lumineux [Termes IGN] géomètrie algorithmique [Termes IGN] gradient de pente [Termes IGN] modèle atmosphérique [Termes IGN] modèle numérique de surface [Termes IGN] Mont-Blanc, massif du [Termes IGN] montagne [Termes IGN] pente [Termes IGN] rayonnement solaire Résumé : (Auteur) Terrain parameters derived from digital elevation models (DEMs), such as slope gradient, aspect and cell surface area, are represented as a vector normal to the surface and calculated using the minimum areal unit of the DEM, that is enclosed between four data points. The position of the Sun is calculated by applying rotational matrices to a unit vector defined at noon as a function of latitude and declination. The direct component of insolation intercepted by the cell surface is then calculated as a dot product between the unit vector in the direction of the Sun and the unit vector normal to surface, multiplied by direct normal irradiation. Hillshading is computed by scanning the projection of cells onto a solar illumination plane perpendicular to the Sun direction. Horizon angles and estimated sky view factor are calculated using a more economical algorithm than a rigorous evaluation of all the angles subtended by every grid cell to each other. The performance of the slope algorithm is evaluated using a synthetic surface and real world examples are given for the Mont Blanc Massif, in the French Alps. Numéro de notice : A2003-102 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/713811744 En ligne : https://doi.org/10.1080/713811744 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22398 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-03011	RAB	Revue	Centre de documentation	En réserve L003	Disponible
079-03012	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Extending GIS-based visual analysis: the concept of visualscapes / M. Llobera in International journal of geographical information science IJGIS, vol 17 n° 1 (february 2003)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 17 n° 1 (february 2003) . - pp 25 - 48 Titre : Extending GIS-based visual analysis: the concept of visualscapes Type de document : Article/Communication Auteurs : M. Llobera, Auteur Année de publication : 2003 Article en page(s) : pp 25 - 48 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications SIG [Termes IGN] données vectorielles [Termes IGN] modèle logique de données [Termes IGN] paysage [Termes IGN] système d'information géographique [Termes IGN] vision [Termes IGN] visualisation 3D Résumé : (Auteur) A Geographical Information System (GIS) is used to retrieve and explore the spatial properties of the visual structure inherent in space. The first section of the article aims to gather, compare and contrast existing approaches used to study visual space and found in disciplines such as landscape architecture, urbanism, geography and landscape archaeology. The concept of a visualscape is introduced in the following section as a tentative unifying concept to describe all possible ways in which the structure of visual space may be defined, broken down and represented within GIS independently of the context in which it is applied. Previous visibility studies in GIS are reviewed and further explored under this new concept. The last section presents the derivation of new visual parameters and introduces a new data structure (i.e. a vector field) to describe the visual exposure of a terrain. Numéro de notice : A2003-103 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/713811741 En ligne : https://doi.org/10.1080/713811741 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22399 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-03011	RAB	Revue	Centre de documentation	En réserve L003	Disponible
079-03012	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Gambling with randomness: the use of pseudo-random number generators in GIS / K. Van Niel in International journal of geographical information science IJGIS, vol 17 n° 1 (february 2003)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 17 n° 1 (february 2003) . - pp 49 - 68 Titre : Gambling with randomness: the use of pseudo-random number generators in GIS Type de document : Article/Communication Auteurs : K. Van Niel, Auteur ; S.W. Laffan, Auteur Année de publication : 2003 Article en page(s) : pp 49 - 68 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications SIG [Termes IGN] analyse spatiale [Termes IGN] méthode de Monte-Carlo [Termes IGN] modèle stochastique [Termes IGN] processus stochastique [Termes IGN] simulation Résumé : (Auteur) Analyses within the field of GIS are increasingly applying stochastic methods and systems that make use of pseudo-random number generators (PRNGs). Examples include Monte Carlo techniques, dynamic modelling, stochastic simulation, artificial life and simulated data development. PRNGs have inherent biases, and this will in turn bias any analyses using them. Therefore, the validity of stochastic analyses is reliant on the PRNG employed. Despite this, the effect of PRNGs in spatial analyses has never been completely explored, particularly a comparison of different PRNGs. Exacerbating the problem is that GIS articles applying Monte Carlo or other stochastic methods rarely report which PRNG is employed. It thus appears likely that GIS researchers rarely, if ever, cheek the suitability of the PRNG employed for their analyses or simulations. This paper presents a discussion of some of the characteristics of PRNGs and specific issues from a geospatial standpoint, including a demonstration of the differences in the results of a Monte Carlo analysis obtained using two different PRNGs. It then makes recommendations for the application of PRNGs in spatial analyses, including recommending specific PRNGs that have attributes appropriate for geospatial analysis. The paper concludes with a call for more research into the application of PRNGs to spatial analyses to fully understand the impact of biases, especially before they are routinely used in the wider spatial analysis community. Numéro de notice : A2003-104 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/713811743 En ligne : https://doi.org/10.1080/713811743 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22400 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
079-03011	RAB	Revue	Centre de documentation	En réserve L003	Disponible
079-03012	RAB	Revue	Centre de documentation	En réserve L003	Disponible