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<TITLE>[UMN_MAPSERVER-USERS] Mutiple "DATA" lines in a single layer?</TITLE>
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<DIV dir=ltr><FONT face=Verdana color=#000000 size=2>as Stephen said, there is
only ONE data statement per layer. But, if you use mapscript, you can change it
dynamically depending on the scale for example</FONT></DIV>
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<FONT face=Tahoma size=2><B>De:</B> UMN MapServer Users List de la part de Jeff
Dege<BR><B>Date:</B> ven. 18/05/2007 20:32<BR><B>À:</B>
MAPSERVER-USERS@LISTS.UMN.EDU<BR><B>Objet :</B> [UMN_MAPSERVER-USERS] Mutiple
"DATA" lines in a single layer?<BR></FONT><BR></DIV>
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<P><FONT size=2>I'm starting to play around with using MapServer to serve maps
from a<BR>PostGIS database.<BR><BR>One of the features that MapServer has is
that you can define multiple<BR>classes within a single layer, so you can change
the way that the map<BR>looks when drawn at different
scales/resolutions.<BR><BR>Is there some way to define multiple data sources
within a single layer,<BR>so that I can change how that data is obtained at
different layers?<BR><BR>In particular, I'm wondering how to best take advantage
of PostGIS's<BR>simplify() function - which can be used to reduce the number of
points<BR>included in a geometry based on resolution. If I'm drawing a map
at a<BR>resolution where one pixel equals 2000 meters on the ground, there is
no<BR>advantage to sending the viewer a geometry defined with
points<BR>twenty-five meters apart.<BR><BR>The obvious way is to define multiple
layers, each enabled at certain<BR>scales, and to include the resulution
appropriate for those scales in<BR>the DATA keyword's sql statement. But
this requires that the layer be<BR>duplicated for each scale range. Is
there a way to enable different<BR>DATA sql statements at different
scales/resolutions in a single layer<BR>definition?<BR><BR>I don't see the DATA
keyword in the documentation for the CLASS section.<BR>Which is where I'd expect
it to be if I could do what I want.<BR><BR>Is there a way of including a value
calculated from the scale in the SQL<BR>statement within the LAYER
section?<BR><BR> DATA "simplify(the_geom, 1.0/<scale>) from
streets"<BR><BR>Or am I stuck with using multiple
layers?<BR><BR></FONT></P></DIV>
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