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Motiejus Jakštys 2021-05-19 22:57:49 +03:00 committed by Motiejus Jakštys
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commit c1515dc1e8
2 changed files with 12 additions and 12 deletions
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Makefile
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@ -176,7 +176,7 @@ salvis-overlaid-visvalingam-64-chaikin-50k_QUADRANT = 1
REF = $(shell git describe --abbrev=12 --always --dirty) REF = $(shell git describe --abbrev=12 --always --dirty)
version.inc.tex: Makefile $(shell git rev-parse --git-dir 2>/dev/null) version.inc.tex: Makefile $(shell git rev-parse --git-dir 2>/dev/null)
TZ=UTC date '+\gdef\VCDescribe{%F ($(REF))}%' > $@ TZ=UTC date '+\gdef\VCDescribe{%F (revision $(REF))}%' > $@
vars.inc.tex: vars.awk wm.sql Makefile vars.inc.tex: vars.awk wm.sql Makefile
awk -f $< wm.sql awk -f $< wm.sql

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mj-msc.tex
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@ -91,12 +91,11 @@
\label{sec:abstract} \label{sec:abstract}
Currently available line simplification algorithms are rooted in mathematics Currently available line simplification algorithms are rooted in mathematics
and geometry, and are not fit bendy natural features like rivers and and geometry, and are unfit for natural features like rivers and
coastlines. This paper discusses our implementation of {\WM} algorithm, coastlines. {\WM} algorithm is derived from cartographic knowledge, and
with notes that we would have been appreciated before starting the thus is well suited for natural features. We also documented our
re-implementation endeavor. This paper accompanies our implementation of implementation, which allows anyone understand the algorithm and our
{\WM} algorithm and will be helpful to anyone trying to understand the implementation in detail.
original {\WM} paper, or our implementation.
\end{abstract} \end{abstract}
@ -120,18 +119,19 @@ Textwidth in cm: {\printinunitsof{cm}\prntlen{\textwidth}}
When creating small-scale maps, often the detail of the data source is greater When creating small-scale maps, often the detail of the data source is greater
than desired for the map. While many features can be removed or simplified, it than desired for the map. While many features can be removed or simplified, it
is more tricky with natural features that have many bends, like coastlines, is more tricky with natural features that have many bends, like coastlines,
rivers and forest boundaries. rivers or forest boundaries.
To create a small-scale map from a large-scale data source, features need to be To create a small-scale map from a large-scale data source, features need to be
generalized: detail should be reduced. While performing the generalization, it generalized, i.e. detail should be reduced. While performing the generalization, it
is important to retain the "defining" shape of the original feature. Otherwise, is important to retain the "defining" shape of the original feature. Otherwise,
if the generalized feature looks too different than the original, the result if the generalized feature looks too different than the original, the result
will look unrealistic. will look unrealistic.
For example, if a river is nearly straight, it should be nearly straight after For example, if a river is nearly straight, it should be nearly straight after
generalization, otherwise a too straightened river will look like a canal. generalization. A too straightened river will look like a canal, and the other
Conversely, if the river is highly wiggly, the number of bends should be way around --- too curvy would not reflect the natural shape. Conversely, if
reduced, but not removed altogether. the river is highly wiggly, the number of bends should be reduced, but not
removed altogether.
Generalization problem for other objects can often be solved by other Generalization problem for other objects can often be solved by other
non-geometric means: non-geometric means: