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Alfred Melch 2019-08-05 13:38:04 +02:00
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thesis/chapters/02.02-Dataformats.tex
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\subsection{Geodata formats on the Web}
\label{ch:dataformats}
Here the data formats that are used through this theses will be explained.

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thesis/chapters/03.01-benchmark.tex
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\label{sec:simplify.js}
% Simplify.JS + turf
Simplify.js calls itself a "tiny high-performance JavaScript polyline simplification library"\footnote{\path{https://mourner.github.io/simplify-js/}}. It was extracted from Leaflet, the "leading open-source JavaScript library for mobile-friendly interactive maps"\footnote{\path{https://leafletjs.com/}}. Due to its usage in leaflet and Turf.js, a geospatial analysis library, it is the most common used library for polyline simplification. The library itself currently has 20,066 weekly downloads while the Turf.js derivate @turf/simplify has 30,389. Turf.js maintains an unmodified fork of the library in its own repository. \todo{So numbers can be added} \todo{leaflet downloads}
Simplify.js calls itself a "tiny high-performance JavaScript polyline simplification library"\footnote{\path{https://mourner.github.io/simplify-js/}}. It was extracted from Leaflet, the "leading open-source JavaScript library for mobile-friendly interactive maps"\footnote{\path{https://leafletjs.com/}}. Due to its usage in leaflet and Turf.js, a geospatial analysis library, it is the most common used library for polyline simplification. The library itself currently has 20,066 weekly downloads while the Turf.js derivate @turf/simplify has 30,389. Turf.js maintains an unmodified fork of the library in its own repository. \todo{leaflet downloads}
The Douglas-Peucker algorithm is implemented with an optional radial distance preprocessing routine. This preprocessing trades performance for quality. Thus the mode for disabling this routine is called highest quality.
Interestingly the library expects coordinates to be a list of object with x and y properties. \todo{reference object vs array form} GeoJSON and TopoJSON however store coordinates in nested array form. Luckily since the library is small and written in JavaScript any skilled web developer can easily fork and modify the code for his own purpose. This is even pointed out in the source code. The fact that Turf.js, which can be seen as a convenience wrapper for processing GeoJSON data, decided to keep the library as is might indicate some benefit to this format. Listing \ref{lst:turf-transformation} shows how Turf.js calls Simplify.js. Instead of altering the source code the data is transformed back and forth between the formats on each call. It is questionable if this practice is advisable at all.
Interestingly the library expects coordinates to be a list of object with x and y properties. GeoJSON and TopoJSON however store coordinates in nested array form (see chapter \ref{ch:dataformats}). Luckily since the library is small and written in JavaScript any skilled web developer can easily fork and modify the code for his own purpose. This is even pointed out in the source code. The fact that Turf.js, which can be seen as a convenience wrapper for processing GeoJSON data, decided to keep the library as is might indicate some benefit to this format. Listing \ref{lst:turf-transformation} shows how Turf.js calls Simplify.js. Instead of altering the source code the data is transformed back and forth between the formats on each call. It is questionable if this practice is advisable at all.
\lstinputlisting[
float=htbp,

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thesis/main.pdf
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