Return the scale factor that converts from meters to other spatial scales
sFactor = ieUnitScaleFactor(unitName)
Valid unit names are
{'nm','nanometer''nanometers'}
{'micron','micrometer','um','microns'}
{'mm','millimeter','millimeters'}
{'cm','centimeter','centimeters'}
{'m','meter','meters'}
{'km','kilometer','kilometers'}
{'inches','inch'}
{'foot','feet'}
This routine is used in various sceneGet/Set and oiGet/Set operations and
oiSpatialSupport. By using this routine, we can specify the units for
various returned quantities.
Copyright ImagEval Consultants, LLC, 2005.