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expand on VW and DP deficiencies

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@ -35,7 +35,7 @@
\title{ \title{
\includegraphics[width=60mm]{vu.png}\\[8ex] \includegraphics[width=60mm]{vu.png}\\[8ex]
Cartographic Generalization of Lines using free software \\ Cartographic Generalization of Lines using free software \\
(example of rivers) \\ \vspace{4mm} (example of rivers)
} }
\author{Motiejus Jakštys} \author{Motiejus Jakštys}
@ -45,11 +45,11 @@
} }
\begin{document} \begin{document}
\maketitle \clearpage\maketitle
\thispagestyle{empty}
\begin{abstract} \begin{abstract}
\label{sec:abstract} \label{sec:abstract}
Current open-source line generalization solutions have their roots in Current open-source line generalization solutions have their roots in
mathematics and geometry, and are not fit for natural objects like rivers mathematics and geometry, and are not fit for natural objects like rivers
and coastlines. This paper discusses our implementation of {\WM} algorithm and coastlines. This paper discusses our implementation of {\WM} algorithm
@ -116,15 +116,34 @@ The "classical" ones are {\DP} and {\VW}.
\cite{douglas1973algorithms} and \cite{visvalingam1993line} are "classical" \cite{douglas1973algorithms} and \cite{visvalingam1993line} are "classical"
line generalization computer graphics algorithms. They are relatively simple to line generalization computer graphics algorithms. They are relatively simple to
implement, require few runtime resources. Both of them accept only a single implement, require few runtime resources. Both of them accept only a single
parameter, which makes them very simple to adjust for different scales. parameter, based on desired scale of the map, which makes them very simple to
adjust for different scales.
However, both of them are emitting insufficient Both algorithms are part of PostGIS, a free-software GIS suite:
\begin{itemize}
\item \cite{douglas1973algorithms} via
\href{https://postgis.net/docs/ST_Simplify.html}{PostGIS Simplify}.
\item \cite{visvalingam1993line} via
\href{https://postgis.net/docs/ST_SimplifyVW.html}{PostGIS SimplifyVW}.
\end{itemize}
Since both algorithms produce jagged output lines, it is worthwhile to process
those through a widely available \cite{chaikin1974algorithm} smoothing
algorithm via \href{https://postgis.net/docs/ST_ChaikinSmoothing.html}{PostGIS
ChaikinSmoothing}.
Even though {\DP} and {\VW} are simple to understand and computationally
efficient, they have serious deficiencies for cartographic natural line
generalization.
<TODO: expand on deficiencies>
\subsection{Modern approaches} \subsection{Modern approaches}
After {\DP} and {\VW} have been established, Due to their simplicity and ubiquity, {\DP} and {\VW} have been established as
go-to algorithms for line generalization. During recent years, more modern
These fall into two rough categories: replacement algorithms have emerged. These fall into roughly two categories:
\begin{itemize} \begin{itemize}
\item Cartographic knowledge was encoded to an algorithm (bottom-up \item Cartographic knowledge was encoded to an algorithm (bottom-up
@ -134,35 +153,20 @@ These fall into two rough categories:
\cite{mustafa2006dynamic}, \cite{nollenburg2008morphing}. \cite{mustafa2006dynamic}, \cite{nollenburg2008morphing}.
\end{itemize} \end{itemize}
During research for the mentioned articles, prototype code has been written for Authors of most of the aforementioned articles have implemented the
most of the algorithms. However, none of them seem to be available for use generalization algorithm, at least to generate the visuals in the articles.
except for the two "classical" ones -- {\DP} and {\VW}. However, I wasn't able to find code for any of those to evaluate with my
desired data set, or use as a basis for my own maps. \cite{wang1998line} is
available in a commercial product.
\cite{wang1998line} is an algorithm specifically created for cartographic The lack of robust openly available generalization algorithm implementations
generalization and available for general use, though it is only currently poses a problem for map creation with free software: there is not a similar
available in a commercial product. This poses a problem for map creation in high-quality simplification algorithm to create down-scaled maps, so any
open source software: there is not a similar high-quality simplification cartographic work, which uses line generalization as part of its processing,
algorithm to create down-scaled maps, so any cartographic work, which uses line will be of sub-par quality. We believe that availability of high-quality
generalization as part of its processing, will be of sub-par quality. open-source tools is an important foundation for future cartographic
We believe that availability of high-quality open-source tools is an important experimentation and development, thus it it benefits the cartographic society
foundation for future cartographic experimentation and development, thus it as a whole.
it benefits the cartographic society as a whole.
This paper will be reviewing and comparing two widely available algorithms that
are often used for line generalization:
\begin{itemize}
\item \cite{douglas1973algorithms} via
\href{https://postgis.net/docs/ST_Simplify.html}{PostGIS Simplify}.
\item \cite{visvalingam1993line} via
\href{https://postgis.net/docs/ST_SimplifyVW.html}{PostGIS SimplifyVW}.
\end{itemize}
Since both algorithms produce jaggy output lines, it is worthwhile to process
those through a widely available \cite{chaikin1974algorithm} smoothing
algorithm via \href{https://postgis.net/docs/ST_ChaikinSmoothing.html}{PostGIS
ChaikinSmoothing}.
\section{Methodology} \section{Methodology}
\label{sec:methodology} \label{sec:methodology}