Default Scale?

[Steve Lime]

You didn't say if you are using MapScript, the CGI or what. I'll assume MapScript
based on context.

Scale is such an arbitrary thing with web-based mapping. You definitely can't
set SCALE within the mapObj and hope things work. Instead you'll probably need
to compute an extent based on a point and a scale value. To do this you need a couple
of pieces of info:

1) the number of pixels per inch of the output device, MapServer uses 72 internally
2) the number of inches per map unit: for meters that value would be 39.3701