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List: mapserver-users
Subject: Re: [mapserver-users] the lines one above other
From: "Rahkonen Jukka (MML)" <jukka.rahkonen () maanmittauslaitos ! fi>
Date: 2015-02-13 9:51:08
Message-ID: b67e3dbad2294cdf9d171945fbbba163 () C119S212VM022 ! msvyvi ! vaha ! local
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Hi,
With OSM and Mapnik it is a two phase process. First osm2pgsql tries to generate \
sensible z-index values and then Mapnik makes "order by" queries to the database. The \
queries are here https://github.com/gravitystorm/openstreetmap-carto/blob/master/project.yaml \
and as an example
(SELECT way,
COALESCE((
'highway_' || (CASE WHEN highway IN ('residential', 'unclassified', 'pedestrian', \
'service', 'footway', 'cycleway', 'track', 'path', 'platform') THEN highway ELSE NULL \
END)), ('railway_' || (CASE WHEN railway IN ('platform') THEN railway ELSE NULL END))
) AS feature
FROM planet_osm_polygon
WHERE highway IN ('residential', 'unclassified', 'pedestrian', 'service', 'footway', \
'track', 'path', 'platform') OR railway IN ('platform')
ORDER BY z_order, way_area DESC
) AS highway_area_casing
-Jukka Rahkonen-
Vladimir wrote:
Bobb
Thanks you very much for detailed answer.
I'll have to place the parts of lines in various layers.
There is no other elegant decision as i understood, but I wonder how "web-map-giants" \
like GOOGLE or OSM get out of this scrape.
Vladimir,
I've faked this in the past by drawing the same layer many times in one pass (inside \
of the same mapfile), you need at least one complete layer pass, with other partial \
layers for the over/under situations. You can do the partial layer grouping with \
attributes on the segments that need to go under or over, and this is a manual \
process for the most part, but it's a real pain to keep that up to date over time \
(I'm talking over years) . I could probably find a programmer that thought of this \
as a challenge, but you still need a human to decide what is over something else as a \
last QA.
The much harder task is defining which layers (partial segments are over/under other \
layers.. You need to remove some line segments form at least one of the layers in \
order to make things display correctly. Sometimes a layer is over, sometime it's \
under. I actually have two instances in my mapping system, where I have three \
different bridges stacked on top of each other, two of them a roadways, with the odd \
one in between them. The other has a Railway bridge over a roadway bridge crossing.
The z-index stuff has always been a painful thing thing to keep updated, but it is \
doable.
I've rencetly been looking at this myself for hardcopy pringing purposes. As well.
Bobb
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<p class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">With \
OSM and Mapnik it is a two phase process. First osm2pgsql tries to generate sensible \
z-index values and then Mapnik makes "order by" queries to the database. The queries \
are here <a href="https://github.com/gravitystorm/openstreetmap-carto/blob/master/project.yaml">
https://github.com/gravitystorm/openstreetmap-carto/blob/master/project.yaml</a> and \
as an example<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">(SELECT \
way,<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">COALESCE((<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">'highway_' \
|| (CASE WHEN highway IN ('residential', 'unclassified', 'pedestrian', 'service', \
'footway', 'cycleway', 'track', 'path', 'platform') THEN highway ELSE NULL \
END)),<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">('railway_' \
|| (CASE WHEN railway IN ('platform') THEN railway ELSE NULL \
END))<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">) \
AS feature<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">FROM \
planet_osm_polygon<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">WHERE \
highway IN ('residential', 'unclassified', 'pedestrian', 'service', 'footway', \
'track', 'path', 'platform')<o:p></o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">OR \
railway IN ('platform')<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">ORDER \
BY z_order, way_area DESC<o:p></o:p></span></p> <p class="MsoNormal"><span \
lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">) \
AS highway_area_casing<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Jukka \
Rahkonen-<o:p></o:p></span></p> <p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><span lang="EN-US" \
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Vladimir \
wrote:<o:p></o:p></span></p> </div>
</div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p><span lang="EN-US">Bobb<o:p></o:p></span></p>
<p><span lang="EN-US">Thanks you very much for detailed answer.<br>
I'll have to place the parts of lines in various layers.<br>
There is no other ele</span>gant decision as i understood, but I wonder how \
"web-map-giants" like GOOGLE or OSM get out of this scrape.<o:p></o:p></p> \
<blockquote style="border:none;border-left:solid #0857A6 1.0pt;padding:0cm 0cm 0cm \
8.0pt;margin-left:7.5pt;margin-top:7.5pt;margin-right:7.5pt;margin-bottom:7.5pt"> <p \
class="MsoNormal"><o:p> </o:p></p> <div id="">
<div>
<div>
<div id="style_14237548520000000350_BODY">
<div>
<p><span style="font-size:8.0pt;font-family:"Comic Sans \
MS"">Vladimir,</span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans \
MS""> </span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans MS"">I've faked this in the \
past by drawing the same layer many times in one pass (inside of the same mapfile), \
you need at least one complete layer pass, with other partial layers for the \
over/under situations. You can do the partial layer grouping with attributes \
on the segments that need to go under or over, and this is a manual process for the \
most part, but it's a real pain to keep that up to date over time (I'm talking over \
years) . I could probably find a programmer that thought of this as a \
challenge, but you still need a human to decide what is over something else as a last \
QA.</span><o:p></o:p></p> <p><span style="font-size:8.0pt;font-family:"Comic \
Sans MS""> </span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans MS"">The much harder task is \
defining which layers (partial segments are over/under other layers.. You need \
to remove some line segments form at least one of the layers in order to make things \
display correctly. Sometimes a layer is over, sometime it's under. I \
actually have two instances in my mapping system, where I have three different \
bridges stacked on top of each other, two of them a roadways, with the odd one in \
between them. The other has a Railway bridge over a roadway bridge \
crossing.</span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans \
MS""> </span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans MS"">The z-index stuff has \
always been a painful thing thing to keep updated, but it is \
doable.</span><o:p></o:p></p> <p><span style="font-size:8.0pt;font-family:"Comic \
Sans MS""> </span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans MS"">I've rencetly been \
looking at this myself for hardcopy pringing purposes. As well.</span><o:p></o:p></p> \
<p><span style="font-size:8.0pt;font-family:"Comic Sans \
MS""> </span><o:p></o:p></p> <p><span \
style="font-size:8.0pt;font-family:"Comic Sans \
MS"">Bobb </span><o:p></o:p></p> </div>
</div>
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</div>
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