WMS Scale hint insight

Travis Kirstine tkirstine at JDBARNES.COM
Wed Mar 21 15:22:52 EDT 2007


Hi All,
I was hoping someone could provide some insight into minscale / maxscale and
wms scalehints.

In my mapfile I have defined the scales as:

   LAYER
      NAME "6km_tiles"
      TILEINDEX "6km_tiles/6km_tindex"
      TILEITEM "location"
      METADATA
         "wms_title" "6km Tiles"
      END
      PROJECTION
         "init=epsg:26917" # utm nad 83 zone 17
      END
      TYPE RASTER
      STATUS OFF
      MAXSCALE 250000
      MINSCALE 10000
   END

and in my get capabilities request the layer / scale hints are defined as:

    <Layer queryable="0" opaque="0" cascaded="0">
        <Name>6km_tiles</Name>
        <Title>6km Tiles</Title>
        <SRS>EPSG:26917</SRS>
        <ScaleHint min="4.98902848429637" max="124.725712107409" />
    </Layer>

and when I view the data as a client with the scales are defined as:

   max = 1:333,332
   min = 1:13,333

How do these all relate? Why does the client's min/max scale "respect"
scales defined in the mapfile?  How are the scalehints calculated?

Any insight would be great.

Thanks,

Travis Kirstine
First Base Solutions Limited
Markham, ON
Canada



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