commit 98af1545260a87f49773acd19d073a4fb03402be (tree)
parent 493d43f6b8e7862c9729879ec6cd9aafe3aa0bf5
Author: Motiejus Jakštys <motiejus@uber.com>
Date: Sat, 15 May 2021 00:31:41 +0300
test harness
Diffstat:
6 files changed, 121 insertions(+), 15 deletions(-)
diff --git a/IV/bib.bib b/IV/bib.bib
@@ -228,3 +228,24 @@
url={https://github.com/motiejus/wm},
urldate={2021-05-19},
}
+
+@online{openstreetmap,
+ author={OpenStreetMap contributors},
+ title={Project that creates and distributes free world's geographic data},
+ url={https://www.openstreetmap.org},
+ urldate={2021-05-15},
+ }
+
+@online{nzt,
+ author={Nacionalinė Žemės Tarnyba Prie Žemės Ūkio Ministerijos},
+ title={Atviri Duomenys},
+ url={http://nzt.lt/go.php/lit/Atviri-duomenys},
+ urldate={2021-05-15},
+ }
+
+@online{openmapwm,
+ author={Tomas Straupis},
+ title={Test harness for Wang--M{\"u}ller algorithm},
+ url={https://dev.openmap.lt/webgl/wm.html},
+ urldate={2021-05-15},
+}
diff --git a/IV/mj-msc.tex b/IV/mj-msc.tex
@@ -909,11 +909,20 @@ When debug mode is turned off (that is, \textsc{dbgname} is left unspecified),
\subsection{Merging pieces of the river into one}
-% TODO
-
-NOTE: explain how different river segments are merged into a single line. This
-is not explained in the {\WM} paper, but is a necessary prerequisite. This is
-implemented in \textsc{aggregate-rivers.sql}.
+Example river geometries were sourced from OpenStreetMap\cite{openstreetmap}
+and NŽT\cite{nzt}. Rivers in both data sources are stored in shorter line
+segments, and multiple segments (usually hundreds or thousands for significant
+rivers) define one full river. While it is convenient to store and edit, these
+segments are not explicitly related to each other. This poses a problem for
+simplification algorithms, which manipulate on full linear features at a time:
+full river geometries, but not their parts.
+
+Since these rivers do not have an explicit relationship to connect them
+together, they were connected using heuristics: if two line segments share a
+name and are within 500 meters from each other, then they form a single river.
+For all line simplification algorithms, all rivers need to be combined, and
+this way proved to be reasonably effective. Source code for this operation can
+be found in listings~\onpage{lst:aggregate-rivers.sql}.
\subsection{Bend scaling and dimensions}
\label{sec:bend-scaling-and-dimensions}
@@ -1002,7 +1011,7 @@ but with bends colored as polygons: each color is a distinctive bend.
\centering
\includegraphics[width=\textwidth]{fig8-definition-of-a-bend}
- \caption{similar to figure 8 in \cite{wang1998line}: detected bends are
+ \caption{Similar to figure 8 in \cite{wang1998line}: detected bends are
highlighted.}
\label{fig:fig8-definition-of-a-bend}
@@ -1031,7 +1040,7 @@ when a single vertex is moved outwards the end of the bend.
\includegraphics[width=\textwidth]{fig5-gentle-inflection-after}
\caption{After applying the inflection rule.}
\end{subfigure}
- \caption{figure 5 in \cite{wang1998line}: gentle inflections at the ends of
+ \caption{Figure 5 in \cite{wang1998line}: gentle inflections at the ends of
the bend.}
\label{fig:fig5-gentle-inflection}
\end{figure}
@@ -1347,7 +1356,8 @@ isolated bends are exaggerated, and some small bends are removed.
\label{fig:salvis-wm-220-250k}
\end{figure}
-% TODO: expand
+% TODO: expand section and remove clear-page.
+\clearpage
\subsection{Generalization result comparison with national spatial data sets}
@@ -1355,9 +1365,28 @@ isolated bends are exaggerated, and some small bends are removed.
\subsection{Testing results online}
-% TODO: [Siūlau įdėti nuorodą į web app, kur būtų galima interaktyviai
-% pastestuoti rezultatus. Jeigu planuotum dėti, tuomet galima nedidelį poskyrį
-% pridėti Testing Results]
+An on-line tool\cite{openmapwm} has been developed to test incoming parameters
+to {\WM} algorithm. A user should select a river of interest, enter the
+\textsc{dhalfcircle} parameter and click "Submit". The simplified line feature
+will be overlaid on top of the map.
+
+Figure~\ref{fig:openmap-wm-good} illustrates the end result that looks
+reasonably well. Figure~\ref{fig:openmap-wm-bad} illustrates that the algorithm
+produces poorly simplified results for some geometries.
+
+\begin{figure}[ht]
+ \centering
+ \includegraphics[width=\textwidth]{openmap-wm-good.png}
+ \caption{Example on-line test tool for {\WM} algorithm.}
+ \label{fig:openmap-wm-good}
+\end{figure}
+
+\begin{figure}[ht]
+ \centering
+ \includegraphics[width=.5\textwidth]{openmap-wm-bad.png}
+ \caption{Another example from the on-line test tool.}
+ \label{fig:openmap-wm-bad}
+\end{figure}
\section{Conclusions}
\label{sec:conclusions}
diff --git a/IV/openmap-wm-bad.png b/IV/openmap-wm-bad.png
Binary files differ.
diff --git a/IV/openmap-wm-good.png b/IV/openmap-wm-good.png
Binary files differ.
diff --git a/IV/vars.awk b/IV/vars.awk
@@ -10,7 +10,7 @@ BEGIN { FS="[(); ]" }
x2 += 1;
d2 = sprintf("\\newcommand{\\isolationThreshold}{%.1f}",$7);
}
-/scale constant float default / {
+/scale2 constant float default / {
x3 += 1;
d3 = sprintf("\\newcommand{\\exaggerationEnthusiasm}{%.1f}",$7);
}
diff --git a/IV/wm.sql b/IV/wm.sql
@@ -417,7 +417,9 @@ begin
return st_split(st_snap(input, blade, 0.00000001), blade);
end $$ language plpgsql;
-
+-- wm_exaggerate_bend2 is the second version of bend exaggeration. Uses
+-- non-linear interpolation by point azimuth. Slower, but produces nicer
+-- exaggerated geometries.
drop function if exists wm_exaggerate_bend2;
create function wm_exaggerate_bend2(
INOUT bend geometry,
@@ -425,7 +427,7 @@ create function wm_exaggerate_bend2(
desired_size float
) as $$
declare
- scale constant float default 1.2; -- exaggeration enthusiasm
+ scale2 constant float default 1.2; -- exaggeration enthusiasm
midpoint geometry; -- midpoint of the baseline
points geometry[];
startazimuth float;
@@ -459,7 +461,7 @@ begin
if diffazimuth > 90 then
diffazimuth = 180 - diffazimuth;
end if;
- sss = ((scale-1) * (diffazimuth / 90)^0.5);
+ sss = ((scale2-1) * (diffazimuth / 90)^0.5);
point = st_transform(
st_project(
st_transform(point, 4326)::geography,
@@ -472,6 +474,60 @@ begin
end loop;
end $$ language plpgsql;
+-- wm_exaggerate_bend exaggerates a given bend. Uses naive linear
+-- interpolation. Faster than wm_exaggerate_bend2, but result visually looks
+-- worse.
+drop function if exists wm_exaggerate_bend;
+create function wm_exaggerate_bend(
+ INOUT bend geometry,
+ size float,
+ desired_size float
+) as $$
+declare
+ scale constant float default 1.2; -- exaggeration enthusiasm
+ midpoint geometry; -- midpoint of the baseline
+ splitbend geometry; -- bend split across its half
+ bendm geometry; -- bend with coefficients to prolong the lines
+ points geometry[];
+begin
+ if size = 0 then
+ raise 'invalid input: zero-area bend';
+ end if;
+ midpoint = st_lineinterpolatepoint(st_makeline(
+ st_pointn(bend, 1),
+ st_pointn(bend, -1)
+ ), .5);
+
+ while size < desired_size loop
+ splitbend = wm_st_split(bend, st_lineinterpolatepoint(bend, .5));
+ -- Convert bend to LINESTRINGM, where M is the fraction by how
+ -- much the point will be prolonged:
+ -- 1. draw a line between midpoint and the point on the bend.
+ -- 2. multiply the line length by M. Midpoint stays intact.
+ -- 3. the new set of lines form a new bend.
+ -- Uses linear interpolation; can be updated to gaussian or similar;
+ -- then interpolate manually instead of relying on st_addmeasure.
+ bendm = st_collect(
+ st_addmeasure(st_geometryn(splitbend, 1), 1, scale),
+ st_addmeasure(st_geometryn(splitbend, 2), scale, 1)
+ );
+
+ points = array((
+ select st_scale(
+ st_makepoint(st_x(geom), st_y(geom)),
+ st_makepoint(st_m(geom), st_m(geom)),
+ midpoint
+ )
+ from st_dumppoints(bendm)
+ order by path[1], path[2]
+ ));
+
+ bend = st_setsrid(st_makeline(points), st_srid(bend));
+ size = wm_adjsize(bend);
+ end loop;
+end $$ language plpgsql;
+
+
-- wm_adjsize calculates adjusted size for a polygon. Can return 0.
drop function if exists wm_adjsize;
create function wm_adjsize(bend geometry, OUT adjsize float) as $$
