Thanks, Jukka. Unfortunately, I'm stuck with Shapefiles. Postgis isn't an option right now. I did manage to come up with a solution using OpenLayers and several Layer definitions in my map file. Each layer points to the same Shapefile, but with a different geomtransform. I use OpenLayers to choose the right map layer based on the map zoom/scale.
> On Jul 22, 2014, at 4:32 PM, "Rahkonen Jukka (Tike)" > <[email protected]> wrote: > > Hi, > > For my mind WFS delivers vector data who do not really have any scale but you > may have some idea about how you define the scale. Perhaps like "Send me > vectors for the same area than my raster background map which comes from WMS > and has a scale of 1:x". However, I do not believe that WFS server can > compute anything like scale from the standard WFS GetFeature parameters > because equivalent to raster pixel size is missing. > > Have you considered to use variable substitution by reading the data from > PostGIS or Spatialite, defining DATA as "select > ST_Simplify(geometry,%tolerance%) as geometry,..." and make your application > to send the tolerance variable with GetFeature requests? Make it to compute > the tolerance by for example the width of BBOX if you use it in your > GetFeatures. > > -Jukka Rahkonen- > > Tom wrote: > > Hi folks, > > I’m trying to implement a kind of ‘feature generalization’ so that the > feature data in my WFS responses will be appropriate to the map zoom level. > I see two basic techniques I could use to do this: > > 1) Use different shapefiles at different zoom levels > 2) Use GEOMTRANSFORM somehow > > Of these two, GEOMTRANSFORM seems like the least hassle. However, I can’t > seem to figure out a way to factor in my map’s scale into the amount of shape > simplification. When I’m zoomed out, the shapes should be simplified a lot. > When I’m zoomed the whole way in, I should be using finer detail. Is there a > variable I can use in this expression? GEOMTRANSFORM (simplifypt([shape], > [map_cellsize] * 10)) > > [map_scale] would be nice, if it existed. > > > > Thanks, > > Tom > _______________________________________________ > mapserver-users mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/mapserver-users
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