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Regression modeling of reduction in spatial accuracy and detail for multiple geometric line simplification procedures / Timofey Samsonov in International journal of cartography, Vol 6 n° 1 (March 2020)  

Public [article]  inInternational journal of cartography > Vol 6 n° 1 (March 2020) . - pp 47 - 70 Titre : Regression modeling of reduction in spatial accuracy and detail for multiple geometric line simplification procedures Type de document : Article/Communication Auteurs : Timofey Samsonov, Auteur ; Olga P. Yakimova, Auteur Année de publication : 2020 Article en page(s) : pp 47 - 70 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme de Douglas-Peucker [Termes IGN] algorithme de Visvalingam [Termes IGN] modèle de régression [Termes IGN] niveau de détail [Termes IGN] précision cartographique [Termes IGN] représentation des détails topographiques [Termes IGN] simplification de contour [Vedettes matières IGN] Généralisation Résumé : (auteur) One of the important stages of map generalization is the selection of optimal simplification procedure for each spatial feature or feature type. Selected algorithms are then applied collaboratively to simplify the whole set of features. However, there is a lack of investigations that report a systematic approach of deriving a similar reduction in accuracy and detail by using different algorithms. In current paper we propose the solution to this problem on the basis of regression modeling between tolerance value of each algorithm and the value of some geometric measure which describes changes in accuracy and detail of the line. This allows fitting the regression model between tolerance values of the two selected algorithms which can be used to obtain similar simplification results. Regressions between Douglas-Peucker, Li-Openshaw and Visvalingam-Whyatt algorithm tolerance values are investigated. Application of methodology is illustrated on the example of three coastlines with significantly different spatial character. Results of the study show that regression coefficients depend highly both on the combination of the two algorithms, and on the character of the line. Finally, it is shown that a weighted combination of accuracy and detail regression models can be used to model the changes in level of detail of the line. Numéro de notice : A2020-071 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/23729333.2019.1615745 Date de publication en ligne : 29/07/2019 En ligne : https://doi.org/10.1080/23729333.2019.1615745 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94634 [article]

Teragons for testing implementations of point reduction algorithms / Mahes Visvalingam in Cartographic journal (the), Vol 55 n° 3 (August 2018)  

Public [article]  inCartographic journal (the) > Vol 55 n° 3 (August 2018) . - pp 256 - 272 Titre : Teragons for testing implementations of point reduction algorithms Type de document : Article/Communication Auteurs : Mahes Visvalingam, Auteur Année de publication : 2018 Article en page(s) : pp 256 - 272 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme de Douglas-Peucker [Termes IGN] algorithme de Visvalingam [Termes IGN] généralisation automatique de données [Termes IGN] simplification de contour [Vedettes matières IGN] Généralisation Résumé : (Auteur) There are several open source and commercial implementations of the Visvalingam algorithm for line generalization. The algorithm provides scope for implementation-specific interpretations, with different outcomes. This is inevitable and sometimes necessary and, it does not imply that an implementation is flawed. The only restriction is that the output must not be so inconsistent with the intent of the algorithm that it becomes inappropriate. The aim of this paper is to place the algorithm within the literature, and demonstrate the value of the teragon-test for evaluating the appropriateness of implementations; Mapshaper v 0.2.28 and earlier versions are used for illustrative purposes. Data pertaining to natural features, such as coastlines, are insufficient for establishing whether deviations in output are significant. The teragon-test revealed an unexpected loss of symmetry from both the Visvalingam and Douglas-Peucker options, making the tested versions unsuitable for some applications, especially outside of cartography. This paper describes the causes, and discusses their implications. Mapshaper 0.3.17 passes the teragon test. Other developers and users should check their implementations using contrived geometric data, such as the teragon data used in this paper, especially when the source code is not available for inspection. The teragon-test is also useful for evaluating other point reduction algorithms. Numéro de notice : A2018-518 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00087041.2017.1414017 Date de publication en ligne : 18/10/2018 En ligne : https://doi.org/10.1080/00087041.2017.1414017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91323 [article]

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Implications of weighting metrics for line generalization with Visvalingam's algorithm / Mahes Visvalingam in Cartographic journal (the), Vol 53 n° 3 (August 2016)  

Public [article]  inCartographic journal (the) > Vol 53 n° 3 (August 2016) . - pp 253 - 267 Titre : Implications of weighting metrics for line generalization with Visvalingam's algorithm Type de document : Article/Communication Auteurs : Mahes Visvalingam, Auteur ; J.C. Whelan, Auteur Année de publication : 2016 Article en page(s) : pp 253 - 267 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme de Visvalingam [Termes IGN] littoral [Termes IGN] métrique [Termes IGN] pondération [Termes IGN] retour d'expérience technique [Termes IGN] simplification de contour [Vedettes matières IGN] Généralisation Résumé : (auteur) Visvalingam's algorithm was designed for caricatural line generalization. A distinction must be made between the algorithm and its operational definition, which includes the metric used to drive it. When the algorithm was first introduced, it was demonstrated using the concept of the effective area of triangles. It was noted that alternative metrics could be used and that the metrics could be weighted, for example to take account of shape. Ordnance Survey (Great Britain) and others are using Visvalingam's algorithm for generalizing coastlines and other natural features, with complex parameter-driven functions to weight the original metric. This paper shows how free software and data were used to scrutinize the implications of one of Matthew Bloch's simple and transparent weighting functions. The results look promising, when compared with manually produced mid and small-scale maps; and encourage further research focussed on weighting functions and related topics, such as self-intersection of lines and model-based generalization. The paper discusses why weights were used in some projects. It comments on their range of applicability and reiterates the original guidance provided for the use of weights. It also demonstrates how weights can undermine the algorithm's capacity to draw caricatures with very few points. The paper provides sufficient background and links to the authors’ test data and to open source software for the benefit of others wishing to undertake research in line generalization using Visvalingam's algorithm. Numéro de notice : A2016-682 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00087041.2016.1149906 En ligne : http://dx.doi.org/10.1080/00087041.2016.1149906 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81942 [article]

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The Visvalingam algorithm: metrics, measures and heuristics / Mahes Visvalingam in Cartographic journal (the), Vol 53 n° 3 (August 2016)  

Public [article]  inCartographic journal (the) > Vol 53 n° 3 (August 2016) . - pp 242 - 252 Titre : The Visvalingam algorithm: metrics, measures and heuristics Type de document : Article/Communication Auteurs : Mahes Visvalingam, Auteur Année de publication : 2016 Article en page(s) : pp 242 - 252 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme de généralisation [Termes IGN] algorithme de Visvalingam [Termes IGN] généralisation cartographique automatisée [Termes IGN] littoral [Termes IGN] méthode heuristique [Termes IGN] métrique [Vedettes matières IGN] Généralisation Résumé : (auteur) This paper provides the background necessary for a clear understanding of forthcoming papers relating to the Visvalingam algorithm for line generalization, for example on the testing and usage of its implementations. It distinguishes the algorithm from implementation-specific issues to explain why it is possible to get inconsistent but equally valid output from different implementations. By tracing relevant developments within the now-disbanded Cartographic Information Systems Research Group (CISRG) of the University of Hull, it explains why (a) a partial metric-driven implementation was, and still is, sufficient for many projects but not for others; (b) why the effective area (EA) is a measure derived from a metric; (c) why this measure (EA) may serve as a heuristic indicator for in-line feature segmentation and model-based generalization; (d) how metrics may be combined to change the order of point elimination; and (e) how Tobler's rule-of-thumb is useful for scale-related filtering of EA. The issues discussed in this paper also apply to the use of other metrics. It is hoped that the background and guidance provided in this paper will enable others to participate in further research based on the algorithm. Numéro de notice : A2016-681 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00087041.2016.1151097 En ligne : http://dx.doi.org/10.1080/00087041.2016.1151097 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81938 [article]

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Simplification and generalization of large scale data for roads: a comparison of two filtering algorithms / M. Visvalingam in Cartography and geographic information systems, vol 22 n° 4 (December 1995)  

Public [article]  inCartography and geographic information systems > vol 22 n° 4 (December 1995) . - pp 264 - 275 Titre : Simplification and generalization of large scale data for roads: a comparison of two filtering algorithms Type de document : Article/Communication Auteurs : M. Visvalingam, Auteur ; P.J. Williamson, Auteur Année de publication : 1995 Article en page(s) : pp 264 - 275 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] algorithme de Douglas-Peucker [Termes IGN] algorithme de filtrage [Termes IGN] algorithme de Visvalingam [Termes IGN] analyse comparative [Termes IGN] généralisation cartographique automatisée [Termes IGN] lissage de courbe [Termes IGN] objet géographique linéaire [Termes IGN] photographie à grande échelle [Termes IGN] réseau routier [Termes IGN] route [Termes IGN] segmentation [Vedettes matières IGN] Généralisation Résumé : (Auteur) This paper reports the results of an indepth study which investigated two algorithms for line simplification and caricatural generalization (namely, those developed by Douglas and Peucker, and Visvalingam, respectively) in the context of a wider program of research on scalefree mapping. The use of largescale data for man-designed objects, such as roads, has led to a better understanding of the properties of these algorithms and of their value within the spectrum of scalefree mapping. The Douglas-Peucker algorithm is better at minimal simplification. The large-scale data for roads makes it apparent that Visvalingam's technique is not only capable of removing entire scale-related features, but that it does so in a manner which preserves the shape of retained features. This technique offers some prospects for the construction of scalefree databases since it offers some scope for achieving balanced generalizations of an entire map, consisting of several complex lines. The results also suggest that it may be easier to formulate concepts and strategies for automatic segmentation of inline features using largescale road data and Visvalingam's algorithm. In addition, the abstraction of center lines may be facilitated by the inclusion of additional filtering rules with Visvalingam's algorithm. Numéro de notice : A1995-007 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1559/152304095782540249 En ligne : https://www.tandfonline.com/doi/abs/10.1559/152304095782540249 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=25737 [article]

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