Scalebar question

[Stéphane RIFF]

Hi,

I have a question about scalebar calculation.
I wrote a map application which is in latlong projection (wgs84)
and mapserver is able to calculate a scale in KM unit, so i would like
to know
how mapserver can do this ???
Does he reproject some points ?
Does the result completly wrong ?

Here is a part of the mapfile :

MAP
    NAME CRN
    STATUS ON
    EXTENT -8.520387 21.998300 12.396365 38.845093
    SIZE 600 600
    IMAGECOLOR 255 255 255
    UNITS DD
    IMAGETYPE PNG
    PROJECTION
      "init=epsg:4326"
    END

    SCALEBAR
        IMAGECOLOR 255 255 255
        LABEL
          COLOR 0 0 255
          SIZE tiny
        END
    STYLE 1
    SIZE 200 2
    COLOR 0 0 255
    UNITS KILOMETERS
    INTERVALS 4
    TRANSPARENT FALSE
    STATUS EMBED
    POSITION LR
    END
END

Maybe i'm completly wrong and this sort of thing isn't realizable but i
want
to know what do you think about that.

Thanks