Η χρήση των αυξομειώσιμων διανυσματικών γραφικών (SVG) στη χαρτογραφική γενίκευση
Creators: name: Κουκουσέλα, Σταματία Κωνσταντίνου
Publisher: name: Aristotle University of Thessaloniki
Year: 2007

description: Η παρούσα μεταπτυχιακή διατριβή έχει ως στόχο να αναδείξει την συμβολή και την χρήση των αυξομειώσιμων διανυσματικών γραφικών (SVG) στην χαρτογραφική γενίκευση. Προσεγγίζει το αντικείμενο της αξιοποίησης ενός σχετικά νέου πρότυπου γνωστού ως Scalable Vector Graphics-SVG, το οποίο αποτελεί μια αποτελεσματική λύση στο πρόβλημα της χαρτογραφικής απόδοσης διδιάστατων διανυσματικών δεδομένων. Αντικειμενικός σκοπός της εργασίας είναι η διερεύνηση του προτύπου SVG, των δυνατοτήτων του, των τεχνικών και αλγορίθμων της χαρτογραφικής γενίκευσης, των ήδη ερευνητικών προγραμμάτων που εστιάζονται στην γενίκευση και κυρίως του αν και πως μπορεί να αποδοθεί ένας γενικευμένος χάρτης με την γλώσσα SVG. Η διεξαγωγή της συγκεκριμένης πειραματικής εφαρμογής, απέδειξε ότι η καλή γνώση και αξιοποίηση του SVG , των μεθόδων και αλγορίθμων γενίκευσης καθώς και ο συνδυασμός αυτών των γνώσεων με γλώσσες προγραμματισμού όπως η Microsoft Visual Basic, η Javascript κ.α. συνεπάγεται τη μετατροπή αυτού σε ένα πολύτιμο εργαλείο για την απόδοση γενικευμένων χαρτών.
description: The present thesis aims at showing the contribution and the use of the Scalable VectorGraphics (SVG) in the cartographical generalization. It deals with the usage of a relativelynew model of ©\the already known©\SVG, which consists an efficient solution to the problem ofthe maping out generalization of the dual©\dimension vector data. The study was carried outduring the Postgraduate Studies Program of Rural and Surveying Engineering of AristotleUniversity of Thessaloniki, ΅°Techniques and Methods for Spatial Analysis, Planning andManagement΅±.The objective goal of the present thesis is the examination of the SVG standard, its potentialsits techniques and algorithms of cartographic generalization, its searching programs whichfocus on the generalization and mainly if and how could be presented a generalized map bythe SVG language.In cartography, the processing, through which a map is converted into a derivative with lowerscale than that of the original, is called ΅®cartographic generalization΅― . The generalizationdescribes the decrease of the complication in a map, it shows elaborately the essentialcharacteristics of space, while©\on the other hand©\ exterminates all of which are not important,preserves the sensible and explicit relationships among the objects of the map and finallymaintains its sensitive quality. The generalization points at creating maps, in a way that theimage of the map to be easily conceivable by the user and the message the map carries to becomprehended.It is widely accepted the confirmation that generalization consists a complicated cartographicalprocess with goals that haven΅―t ¨Cuntil nowadays©\ been defined with a complete and uprightway, because of the subjective factors that determine it. The cartographers, in their exhaustingtry to deal with the unsolved problems of generalization, they have tried methods©\besidesalgorithmic techniques©\which are based on the representation of knowledge and on thesystems that support the decision taking.Mapping represents a perfect apply of SVG, since a map is ‐by its nature‐ a vector formrepresentation of the Earth in different layers.Basically, the SVG is a bridge between the designing and the programming because –unlikethe traditional methods of graphic creation‐ the SVG graphics are made through aprogramming language, the XML, which is compatible with other W3C standards. With theSVG is possible to create simple graphics in just a few text lines. The SVG language setsindividual designs as vectors, which means that the quality of the image remains the same,independently of the scale. The SVG graphics do not lack their quality, when zoomed in orout, moreover they have the privilege of animation. Although the SVG was designed as ageneral graphic language, it can be applied in web‐mapping. All these and several otherreasons force the use of SVG.The cartographical generalization plays a very important role in the basic process of creating amap, in a way that it determines strictly how long it takes to be a map created. But, given thatthe completely automatic generalization is being solved partly as far as it concerns theavailable methods and algorithms, it is necessary to be found other solutions a)for thesubstitution of lacking automated generalization procedures and b)for accelerating technicallyand estimatingly the proper intensive generalization algorithms.The approach which combines the multi scale databases and the cartographical generalizationoffers a possible solution by matching the advantages of both methods. A multi scale databaseis consisted of several data set, which conclude objects stored in different determined scalelevels (e.g. 1:25000, 1:100.000, 1:200.000). These levels (usually called levels of details) areproduced with the contribution of generalizing the total of data set. This specific approach isused in the appliance of this thesis.The chapter structure of the study is the following:Analysis of the cartographic generalization in digital cartography and the use of multiscale database and many representations in generalizationDetailed description of the SVG standard and the presentation/ rendering of vectormaps through this standardApply/Implementation ‐ Representation/rendering of cartographic generalization withSVGConclusionsMore specifically, the present thesis is organized in eight (8) chapters, necessary for thecomplete and indicated development of the subject, in which the theme is as better as possibleanalyzed.The chapters of cartographic generalization in digital cartography and the use of multiscale database and many representations are:This chapter mentions the definitions given until now from various scientists forcartographic generalization in digital cartography, it reports the basic elements of thegeneralization, its operators, as well as it analyses some algorithms of simplifying the line.Chapter 2 ‐ Cartographic generalization for on demand mapping:In this chapter there are given the meaning of the on demand mapping on the web andsome approaches of specific mapping. Also it is being studied the scope of the study of theon demand mapping as well as the complication and the strategy of the generalizingprocedures.Chapter 3 ‐ The use of many representations database (MRDB) and multiscale(MSDB) in cartographic generalization.The third chapter is focusing on the principles of the many representations database andmulti scale, which are used in cartographic generalization. There are presented and someresearching programs which examine and apply these databases.Afterwards, a description of the SVG standard and the presentation/rendering of vectormaps through this standard follow:Chapter 4 ‐ Introduction to the SVGThis chapter is concerned with a brief summary in the appearance and the meaning ofScalable Vector Graphics (SVG), with the cooperation of some companies that support theSVG standard in their products and it deals with the great advantages of it.Chapter 5 ‐ Description of the SVG standardThis chapter is referred to a detailed report on the existent editions of SVG and to thetechnical specifications like the ones given by the Worldwide Web Consortium (W3C).Also, there are being exposed the basic concepts/principles of SVG, the SVG documents’structure and the appliances in industry and generally.Chapter 6 – Presentation/rendering of vector maps through SVGIn the sixth chapter there are presented detailed all the basic geometric elements of SVG ,the coordinate system and its measuring units as well as some ways of creating maps withSVG.In continuation, it follows the procedure of the appliance for the presentation/rendering ofthe cartographic generalization through SVG.Chapter 7 – Apply/Implementation ‐ Presentation/rendering of the cartographicgeneralization through SVG.In the 7th chapter are finally applied the generalization algorithms, the meaning of themulti scale database with the already mentioned levels of details or scale levels and theSVG, for the presentation of generalized maps. The construction process of the algorithmsin Microsoft Visual Basic as well as the SVG code are being analyzed by using also theprogramming language, Javascript. The particular application gives the possibility ofgeneralization an original map into four predetermined scales, giving the chance to theuser to choose himself which of the four available algorithms he likes.Finally, there are presented Conclusions, Suggestions, extras and the bibliography:Chapter 8 ‐ Conclusions ‐ SuggestionsAt the last part of the study there are mentioned totally the basic conclusions that came upafter a vigorous research in the international bibliography. There are reported conclusionsconcerning to the generalization algorithms that were used, to if they are satisfactoryrelatively to their result, there are proposed solutions for every possible problem andfinally how could the application be more automated.In conclusion, we could say that the carrying out of this specific experimental applicationproved that a good knowledge of the new SVG standard, the generalization methods andalgorithms as well as the combination of this knowledge with programming languages, suchas Microsoft Visual Basic and Javascript have as a consequence the regard of it as a valuabletool for presenting/rendering generalized maps by giving the user the chance to choose eachtime the algorithm and scale he likes.