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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I don’t know anything about your work flow, but if
possible, you could add a pre-processing step where you use a script to read
your text file and pre-classify the data. You would end up with integers representing
each class as ‘cell’ values. <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 style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Instead of :<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>EXPRESSION</span>([pixel] >= -4 AND [pixel] < -3)<span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> <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 style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>You could have: EXPRESSION “2” <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Or <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>EXPRESSION /2/<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 style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Matching a single string should be the fastest expression to
evaluate.<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 style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>David.<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>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'>
mapserver-users-bounces@lists.osgeo.org
[mailto:mapserver-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>Tobias
Weiß<br>
<b>Sent:</b> Wednesday, July 28, 2010 8:25 AM<br>
<b>To:</b> mapserver-users@lists.osgeo.org<br>
<b>Subject:</b> Re: [mapserver-users] Raster data performance<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi Alex,<br>
<br>
I tried some of the performance tips you mentioned, e.g. converted the .txt to
a tiled TIFF to optimize performance. I can not see significant changes
in rendering speed.<br>
<br>
gdal_translate -co TILED=YES input.txt output.tif<br>
<br>
The major brake still is the expression stuff. I really wonder what makes this
task so time-consuming, it should not be more than a simple comparison.<br>
<br>
Do you have experiences with this issue? Or do I have to live with this
constraint?<br>
<br>
Best, Tobi<br>
<br>
===<br>
Am 28.07.10 14:27, schrieb Alexandre Dube: <o:p></o:p></p>
<p class=MsoNormal>Hi Tobi,<br>
<br>
The following documentation topics about raster might help :<br>
<br>
<a href="http://mapserver.org/input/raster.html#rasters-and-tile-indexing">http://mapserver.org/input/raster.html#rasters-and-tile-indexing</a><br>
<a href="http://mapserver.org/input/raster.html#raster-display-performance-tips">http://mapserver.org/input/raster.html#raster-display-performance-tips</a><br>
<br>
and about expressions :<br>
<br>
<a href="http://mapserver.org/mapfile/expressions.html">http://mapserver.org/mapfile/expressions.html</a><br>
<br>
The string comparison type is the fastest, so you could try define more
classes but using string comparison to see if it gets faster. Also, a
good performance tip is to put your most frequent classes types on top
first. For example, if 80% of your data has "pixel = -3" then
put it on top.<br>
<br>
Kind regards,<br>
<br>
Alexandre<br>
<br>
<br>
On 10-07-28 04:54 AM, Tobias Weiß wrote: <o:p></o:p></p>
<p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>Hello list,<br>
<br>
this is my first email to this list. I am working with MapServer, OpenLayers
& TileCache for almost 1 year now and the tools are really working great
together, when everything is configured correctly ;-)<br>
<br>
At the moment I´m facing a performance problem with raster data that serves as
input data to render my map tiles. The spatial resolution of this raster data
is 720 (rows) x 360 (cols) and it is stored in a simple .txt file (The size of
the file is around 2 MB). I use TileCache to prerender maptiles for different
zoom levels that are later displayed in a web application using OpenLayers.<br>
<br>
I discovered, that the rendering speed of MapServer seems to mainly depend on
how many different classes I define within my mapfile, meaning how many
expressions MapServer has to evaluate during the rendering process. Without any
classes MapServer the rendering speed is really fast, the more classes I use the
slower it gets. With e.g. 10 different classes defining 10 different styles /
pixel colors the rendering time for one tile can increase up to 60 sec.<br>
<br>
<br>
</span><o:p></o:p></p>
<pre>CLASS<span class=moz-txt-citetags><o:p></o:p></span></pre><pre><span
class=moz-txt-citetags> </span>EXPRESSION ([pixel] >= -4 AND [pixel] < -3)<span
class=moz-txt-citetags><o:p></o:p></span></pre><pre><span
class=moz-txt-citetags> </span>STYLE<o:p></o:p></pre><pre> COLOR 69 117 180<o:p></o:p></pre><pre> END<o:p></o:p></pre><pre>END<o:p></o:p></pre><pre> <o:p></o:p></pre>
<p class=MsoNormal><br>
<span style='font-family:"Tahoma","sans-serif"'>While working with shape files
I haven´t had this problems and prerendering map tiles was really fast. With
raster data the rendering time for one map and 5 different zoom levels can take
up to several hours and almost overburdens my CPU.<br>
<br>
Can anybody give me a hint how I could improve this?<br>
<br>
Best, Tobi<br>
<br>
</span><o:p></o:p></p>
<pre><o:p> </o:p></pre><pre>_______________________________________________<o:p></o:p></pre><pre>mapserver-users mailing list<o:p></o:p></pre><pre><a
href="mailto:mapserver-users@lists.osgeo.org">mapserver-users@lists.osgeo.org</a><o:p></o:p></pre><pre><a
href="http://lists.osgeo.org/mailman/listinfo/mapserver-users">http://lists.osgeo.org/mailman/listinfo/mapserver-users</a><o:p></o:p></pre><pre> <o:p></o:p></pre>
<p class=MsoNormal><br>
<br>
<br>
<o:p></o:p></p>
<pre>-- <o:p></o:p></pre><pre>Alexandre Dubé<o:p></o:p></pre><pre>Mapgears<o:p></o:p></pre><pre><a
href="http://www.mapgears.com">www.mapgears.com</a><o:p></o:p></pre><pre> <o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>_______________________________________________<o:p></o:p></pre><pre>mapserver-users mailing list<o:p></o:p></pre><pre><a
href="mailto:mapserver-users@lists.osgeo.org">mapserver-users@lists.osgeo.org</a><o:p></o:p></pre><pre><a
href="http://lists.osgeo.org/mailman/listinfo/mapserver-users">http://lists.osgeo.org/mailman/listinfo/mapserver-users</a><o:p></o:p></pre><pre> <o:p></o:p></pre></div>
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