Which Projection to use?

[LITTLE Nelson]

Hi all,

I have shape files which are in x,y coordinate form (units of meters)
and didn't think I needed any projection information because I was
dealing with such a small area, thus never defined any PROJECTION info
in my map file. Now I am getting the following error: 

[MapServer Error]: _msProcessAutoProjection(): WMS/WFS AUTO PROJECTION
must be in the format 'AUTO:proj_id,units_id,lon0,lat0' (got '').

I gather from the error message that I need to define at least a map
level projection entry, but I am not sure what I should use?

Any help much appreciated

Cheers,
Nelson

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