fix some of the andriub comments
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IV/mj-msc.tex
111
IV/mj-msc.tex
@ -166,31 +166,47 @@ Given the discussed complexities, a fine line between under-simplification
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to be found. Therein lies the complexity of simplification algorithms: all have
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different trade-offs.
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% TODO:
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% [Magistrinio darbo tikslas - Wang-Müller algoritmo pagrindu realizuoti upių kartografinio generalizavimo sprendimą taikant atviro kodo programinę įrangą.]
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%
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% [Magistro darbo uždaviniai:
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% * Atlikti egzistuojančių linijų supaprastinimo algoritmų vertinimą
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% * Identifikuoti, su kokiomis pagrindinėmis kartografinėmis problemomis susiduriama generalizuojant upes taikant klasikinius geometrijos supaprastinimo agloritmus
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% * Apibrėžti Wang-Müller algoritmo techninės realizacijos metodiką
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% * Realizuoti Wang-Müller algoritmą teoriškai ir techniškai detalizuojant jį sudarančias geometrijos keitimo operacijas
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% * Sukurtą algoritmo prototipą pritaikyti skirtingiems duomenų rinkiniams ir gautus rezultatus palyginti su valstybiniais duomenų rinkiniais]
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%
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% [Mokslinis šio darbo aktualumas - detaliai išnagrinėti, praktiškai įgyvendinti ir aprašyti Wang-Müller algoritmu aprašomi linijų supaprastinimo procesai (žingsniai), kas leidžia išplėsti kartografinės teorijos žinias apie gamtinių objektų ribų generalizavimą atsižvelgiant į jų raiškumą. Wang-Müller straipsnyje, pristatančiame algoritmą, žingsniai sprendiniai nedetalizuojami taip, kad juos būtų galima praktiškai įgyvendinti konkretiems duomenis. Šiame darbe būtent ši dalis ir konkretizuojama. Praktinis šio darbo aktualumas - išplėstos galimybės pasinaudoti atviro kodo programine įranga atlikti kartografinės generalizacijos uždavinius. Sukurtas specializuotas kartografijai linijų supaprastinimo algoritmas gali būti pritaikytas kartografų realizuojant automatinius duomenų generalizavimo sprendimus.
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%
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The purpose of the thesis is to implement a river generalization algorithm
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on the basis of {\WM} algorithm using open-source software.
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Tasks of the thesis:
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\begin{itemize}
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\item Evaluate existing line simplification algorithms.
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\item Identify main river generalization problems using classical line
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simplification algorithms.
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\item Define methods of the {\WM} technical implementation.
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\item Realize {\WM} algorithm technically, explaining the geometric
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transformations in detail.
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\item Apply the created algorithm for different datasets and compare
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the results with national data sets.
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\end{itemize}
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Scientific relevance of this work --- the simplification processes (steps)
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described by the {\WM} algorithm are analyzed in detail, practically
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implemented and the implementation --- described. That expands the knowledge of
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cartographic theory about the generalization of natural objects' boundaries
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after their natural defining properties.
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In the original {\WM} article introducing the algorithm, the steps are not
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detailed in a way that can be put into practice for specific data; steps are
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specified in this work. Practically this work makes it possible to use open
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source software to perform cartographic line generalization. The developed
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specialized cartographic line simplification algorithm can be applied by
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cartographers to implement automatic data generalization solutions. Given the
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open-source nature of this work, the algorithm implementation can be modified
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freely.
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\section{Literature Review and Problematic}
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\label{sec:literature-review-problematic}
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\subsection{Available algorithms}
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TODO: numeracija 2.1(?) gal senas
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This section reviews the classical line simplification algorithms, which,
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besides being around for a long time, offer easily accessible implementations,
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as well as more modern ones, which only theorize, but do not provide an
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implementation.
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\subsubsection{{\DP}, {\VW} and Chaikin's}
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\label{sec:dp-vw-chaikin}
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@ -379,33 +395,23 @@ set, much less for use as a basis for creating new maps. To author's knowledge,
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purchase of the commercial product suite, without a way to license the
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standalone algorithm.
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% TODO BEGIN
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% Ši dalis turi keliauti į problematiką, nes su pačiais algoritmais mažai kuo susiję
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Lack of robust openly available generalization algorithm implementations poses
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a problem for map creation with free software: there is not a similar
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high-quality simplification algorithm to create down-scaled maps, so any
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cartographic work, which uses line generalization as part of its processing,
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will be of sub-par quality. We believe that availability of high-quality
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open-source tools is an important foundation for future cartographic
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experimentation and development, thus it it benefits the cartographic society
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as a whole.
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{\WM}'s commercial availability signals something about the value of the
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algorithm: at least the authors of the commercial software suite deemed it
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worthwhile to include it. However, not everyone has access to the commercial
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software suite, access to funds to buy the commercial suite, or access to the
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operating system required to run the commercial suite. PostGIS, in contrast, is
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free on itself, and runs on free platforms. Therefore, algorithm
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implementations that run on PostGIS or other free platforms are useful to a
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wider cartographic society than proprietary ones.
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% TODO END
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\subsection{Problematic with generalization of rivers}
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% TODO subscection: andriub: Į šį skyrių turi būti perkeltas tekstas iš From Simplification to Generalization ir mano pakomentuota dalis iš Modern approaches skyriaus.
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% DONE subscection: andriub: Į šį skyrių turi būti perkeltas tekstas iš From Simplification to Generalization ir mano pakomentuota dalis iš Modern approaches skyriaus.
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% TODO: [Skyriaus pradžioje pateikiama bendra informacija: Upių generalizavimo problemą galima skaidyti į dvi dalis: egzistuojantys algoritmai skirti geometrijos supaprastinimui, tačiau neturi kartografinės logikos; egzistuojantys sprendimai nėra laisvai prieinami. Atitinkamai tuomet seka tekstas iš From Simplification to Generalization skyriaus, o toliau - dalis iš Modern approaches skyriaus.
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% DONE: [Skyriaus pradžioje pateikiama bendra informacija: Upių generalizavimo problemą galima skaidyti į dvi dalis: egzistuojantys algoritmai skirti geometrijos supaprastinimui, tačiau neturi kartografinės logikos; egzistuojantys sprendimai nėra laisvai prieinami. Atitinkamai tuomet seka tekstas iš From Simplification to Generalization skyriaus, o toliau - dalis iš Modern approaches skyriaus.
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This section introduces the reader to simplification and generalization, and
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discusses two main problems with current-day cartographic line generalization:
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\begin{itemize}
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\item Currently available line simplification algorithms were created
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to simplify geometries, but have no cartographical knowledge.
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\item Existing cartographic line generalization algorithms are not freely
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accessible.
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\end{itemize}
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\subsubsection{Simplification versus Generalization}
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It is important to note the distinction between simplification, line
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generalization and cartographic generalization.
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@ -448,6 +454,28 @@ line generalization deals with a single feature class, but takes into account
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its geographic properties. This paper examines {\WM}'s
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\titlecite{wang1998line}, a cartographic line generalization algorithm.
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\subsubsection{Availablility of generalization algorithms}
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Lack of robust openly available generalization algorithm implementations poses
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a problem for map creation with free software: there is not a similar
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high-quality simplification algorithm to create down-scaled maps, so any
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cartographic work, which uses line generalization as part of its processing,
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will be of sub-par quality. We believe that availability of high-quality
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open-source tools is an important foundation for future cartographic
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experimentation and development, thus it it benefits the cartographic society
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as a whole.
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{\WM}'s commercial availability signals something about the value of the
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algorithm: at least the authors of the commercial software suite deemed it
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worthwhile to include it. However, not everyone has access to the commercial
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software suite, access to funds to buy the commercial suite, or access to the
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operating system required to run the commercial suite. PostGIS, in contrast, is
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free on itself, and runs on free platforms. Therefore, algorithm
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implementations that run on PostGIS or other free platforms are useful to a
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wider cartographic society than proprietary ones.
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\subsubsection{Unfitness of line simplification algorithms}
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Section~\ref{sec:dp-vw-chaikin} illustrates the current gaps with Line
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Simplification algorithms for real rivers. To sum up, we highlight the
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following cartographic problems from our examples:
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@ -463,8 +491,7 @@ following cartographic problems from our examples:
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\end{description}
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We are
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limiting the problem to cartographic line generalization. That is, full
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We are limiting the problem to cartographic line generalization. That is, full
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cartographic generalization, which takes topology and other feature classes
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into account, is out of scope.
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