mapserver rasters scale

[Stéphane RIFF]

Hi all,

I want to display some rasters layers :
       first one is 1/250000, 250 dpi
       second one is 1/25000, 250 dpi

Here is an extract of my map file :
    MAP
       UNITS METERS

       IMAGETYPE PNG

        PROJECTION
          "init=esri:27582"
        END

    LAYER
      NAME "250000"
      TILEINDEX "../data/250000"
      TILEITEM "LOCATION"
      TYPE RASTER
      STATUS ON
      OFFSITE 0 0 0
      MINSCALE 25000
      MAXSCALE 250000
      GROUP "carto"
      CLASS
        NAME "Fond raster 250000"
      END
    END

    LAYER
      NAME "25000"
      TILEINDEX "../data/25000"
      TILEITEM "LOCATION"
      TYPE RASTER
      STATUS ON
      OFFSITE 0 0 0
      MAXSCALE 25000
      GROUP "carto"
      CLASS
        NAME "Fond raster 25000"
      END
    END

This two layer switch well looking for mapserver scale.
The question i want to ask is why when i open a 1/250000 raster with
GIMP and set the scale to 100%,
it doesn't seem to correspond with what i see in mapserver at scale 250000.

In other words, if mapserver scale is 250000, does it means that the
view is at 1/250000 sacle???

I hope my question is understandable
Thanks