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Exploration of information: theoretic arguments for the limited amount of information in a map / J. Bjorke in Cartography and Geographic Information Science, vol 39 n° 2 (April 2012)  

Public [article]  inCartography and Geographic Information Science > vol 39 n° 2 (April 2012) . - pp 88 - 97 Titre : Exploration of information: theoretic arguments for the limited amount of information in a map Type de document : Article/Communication Auteurs : J. Bjorke, Auteur Année de publication : 2012 Article en page(s) : pp 88 - 97 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cartographie [Termes IGN] cartographie par internet [Termes IGN] conception cartographique [Termes IGN] exploration de données [Termes IGN] lisibilité perceptive [Termes IGN] qualité des données [Termes IGN] variable visuelle [Termes IGN] visibilité [Termes IGN] visualisation cartographique Résumé : (Auteur) From the application of information theory capacity limits of maps are derived and some cartographic rules are formulated—based on theoretical models and perception studies. The perception study shows that for a relief map with coloured height intervals the channel capacity, as defined in information theory, is reached at seven~~eight height classes. Generally, the length of a visual variable may be characterized by the channel capacity of the map. This theoretical study shows how increased attention should be paid to perceptual separation as the number of categories increases. The requirement becomes more and more crucial as the number of categories exceeds five. The principle of group visibility is formulated and demonstrated. Group visibility considers the visibility of groups of map features and may be utilized in a visual search for geographical patterns. The quantitative measures presented offers computational methods to control group visibility for example in an interactive visualization system. Numéro de notice : A2012-453 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1559/1523040639288 En ligne : https://doi.org/10.1559/1523040639288 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31899 [article]

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Computation of random errors in digital terrain models / J. Bjorke in Geoinformatica, vol 11 n° 3 (September - November 2007)  

Public [article]  inGeoinformatica > vol 11 n° 3 (September - November 2007) . - pp 359 - 382 Titre : Computation of random errors in digital terrain models Type de document : Article/Communication Auteurs : J. Bjorke, Auteur ; S. Nilsen, Auteur Année de publication : 2007 Article en page(s) : pp 359 - 382 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] analyse comparative [Termes IGN] erreur aléatoire [Termes IGN] filtrage du bruit [Termes IGN] géostatistique [Termes IGN] modèle numérique de terrain [Termes IGN] rééchantillonnage [Termes IGN] sondeur multifaisceaux [Termes IGN] Triangulated Irregular Network [Termes IGN] variogramme Résumé : (Auteur) Geostatistical methods make it possible to estimate the random errors in digital terrain models (DTMs) from one single set of measurements. After average interpolating trend removal, the error is derived from the variogram of the residual data set. This method is compared with a procedure that uses triangulation and resampling of two overlapping DTMs for extracting the error component. Eighteen small areas measured with a multibeam echo sounder are selected for the comparison. In the experiment the two methods come out with similar values for the random error. A by-product of the experiment is the development of a model for the average noise reduction caused by resampling of triangle models (TINs). The method we apply for the trend computation has time complexity O(n). Since the noise computation only requires the part of the variogram close to the origin, it is possible to formulate the computation of the random error in DTMs in O(n) time. Copyright Springer Numéro de notice : A2007-381 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1007/s10707-006-0012-x En ligne : https://doi.org/10.1007/s10707-006-0012-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28744 [article]

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