diff --git a/IV/mj-msc.tex b/IV/mj-msc.tex index 3ed905d..acf67e9 100644 --- a/IV/mj-msc.tex +++ b/IV/mj-msc.tex @@ -166,31 +166,47 @@ Given the discussed complexities, a fine line between under-simplification to be found. Therein lies the complexity of simplification algorithms: all have different trade-offs. -% TODO: -% [Magistrinio darbo tikslas - Wang-Müller algoritmo pagrindu realizuoti upių kartografinio generalizavimo sprendimą taikant atviro kodo programinę įrangą.] -% -% [Magistro darbo uždaviniai: -% * Atlikti egzistuojančių linijų supaprastinimo algoritmų vertinimą -% * Identifikuoti, su kokiomis pagrindinėmis kartografinėmis problemomis susiduriama generalizuojant upes taikant klasikinius geometrijos supaprastinimo agloritmus -% * Apibrėžti Wang-Müller algoritmo techninės realizacijos metodiką -% * Realizuoti Wang-Müller algoritmą teoriškai ir techniškai detalizuojant jį sudarančias geometrijos keitimo operacijas -% * Sukurtą algoritmo prototipą pritaikyti skirtingiems duomenų rinkiniams ir gautus rezultatus palyginti su valstybiniais duomenų rinkiniais] -% -% [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. -% +The purpose of the thesis is to implement a river generalization algorithm +on the basis of {\WM} algorithm using open-source software. + +Tasks of the thesis: + +\begin{itemize} + \item Evaluate existing line simplification algorithms. + \item Identify main river generalization problems using classical line + simplification algorithms. + \item Define methods of the {\WM} technical implementation. + \item Realize {\WM} algorithm technically, explaining the geometric + transformations in detail. + \item Apply the created algorithm for different datasets and compare + the results with national data sets. +\end{itemize} + +Scientific relevance of this work --- the simplification processes (steps) +described by the {\WM} algorithm are analyzed in detail, practically +implemented and the implementation --- described. That expands the knowledge of +cartographic theory about the generalization of natural objects' boundaries +after their natural defining properties. + +In the original {\WM} article introducing the algorithm, the steps are not +detailed in a way that can be put into practice for specific data; steps are +specified in this work. Practically this work makes it possible to use open +source software to perform cartographic line generalization. The developed +specialized cartographic line simplification algorithm can be applied by +cartographers to implement automatic data generalization solutions. Given the +open-source nature of this work, the algorithm implementation can be modified +freely. + \section{Literature Review and Problematic} \label{sec:literature-review-problematic} \subsection{Available algorithms} -TODO: numeracija 2.1(?) gal senas This section reviews the classical line simplification algorithms, which, besides being around for a long time, offer easily accessible implementations, as well as more modern ones, which only theorize, but do not provide an implementation. - - \subsubsection{{\DP}, {\VW} and Chaikin's} \label{sec:dp-vw-chaikin} @@ -379,33 +395,23 @@ set, much less for use as a basis for creating new maps. To author's knowledge, purchase of the commercial product suite, without a way to license the standalone algorithm. -% TODO BEGIN -% Ši dalis turi keliauti į problematiką, nes su pačiais algoritmais mažai kuo susiję - -Lack of robust openly available generalization algorithm implementations poses -a problem for map creation with free software: there is not a similar -high-quality simplification algorithm to create down-scaled maps, so any -cartographic work, which uses line generalization as part of its processing, -will be of sub-par quality. We believe that availability of high-quality -open-source tools is an important foundation for future cartographic -experimentation and development, thus it it benefits the cartographic society -as a whole. - -{\WM}'s commercial availability signals something about the value of the -algorithm: at least the authors of the commercial software suite deemed it -worthwhile to include it. However, not everyone has access to the commercial -software suite, access to funds to buy the commercial suite, or access to the -operating system required to run the commercial suite. PostGIS, in contrast, is -free on itself, and runs on free platforms. Therefore, algorithm -implementations that run on PostGIS or other free platforms are useful to a -wider cartographic society than proprietary ones. - -% TODO END - \subsection{Problematic with generalization of rivers} -% TODO subscection: andriub: Į šį skyrių turi būti perkeltas tekstas iš From Simplification to Generalization ir mano pakomentuota dalis iš Modern approaches skyriaus. +% DONE subscection: andriub: Į šį skyrių turi būti perkeltas tekstas iš From Simplification to Generalization ir mano pakomentuota dalis iš Modern approaches skyriaus. -% 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. +% 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. + +This section introduces the reader to simplification and generalization, and +discusses two main problems with current-day cartographic line generalization: + +\begin{itemize} + \item Currently available line simplification algorithms were created + to simplify geometries, but have no cartographical knowledge. + + \item Existing cartographic line generalization algorithms are not freely + accessible. +\end{itemize} + +\subsubsection{Simplification versus Generalization} It is important to note the distinction between simplification, line generalization and cartographic generalization. @@ -448,6 +454,28 @@ line generalization deals with a single feature class, but takes into account its geographic properties. This paper examines {\WM}'s \titlecite{wang1998line}, a cartographic line generalization algorithm. +\subsubsection{Availablility of generalization algorithms} + +Lack of robust openly available generalization algorithm implementations poses +a problem for map creation with free software: there is not a similar +high-quality simplification algorithm to create down-scaled maps, so any +cartographic work, which uses line generalization as part of its processing, +will be of sub-par quality. We believe that availability of high-quality +open-source tools is an important foundation for future cartographic +experimentation and development, thus it it benefits the cartographic society +as a whole. + +{\WM}'s commercial availability signals something about the value of the +algorithm: at least the authors of the commercial software suite deemed it +worthwhile to include it. However, not everyone has access to the commercial +software suite, access to funds to buy the commercial suite, or access to the +operating system required to run the commercial suite. PostGIS, in contrast, is +free on itself, and runs on free platforms. Therefore, algorithm +implementations that run on PostGIS or other free platforms are useful to a +wider cartographic society than proprietary ones. + +\subsubsection{Unfitness of line simplification algorithms} + Section~\ref{sec:dp-vw-chaikin} illustrates the current gaps with Line Simplification algorithms for real rivers. To sum up, we highlight the following cartographic problems from our examples: @@ -463,8 +491,7 @@ following cartographic problems from our examples: \end{description} -We are -limiting the problem to cartographic line generalization. That is, full +We are limiting the problem to cartographic line generalization. That is, full cartographic generalization, which takes topology and other feature classes into account, is out of scope.