Note that saving windows as registered rasters seems to anchor the NW
corner in the right place, but that there may be slight stretching from
there along both axes, so that in the SE, the corner of the image you
create doesn't necessarily fall exactly where the corner of your mapper
window was. When we save registered images from map windows, the SE
corner of the image consistently falls too far to the SE.
I remember hearing that this has been discussed on the list (though I
haven't looked), so there's probably lots of discussion and ideas about
it in archives. When we first ran into this problem, our solution was
to edit two of the control points (NE and SW) in the .TAB file to
correct the problem. The distortion along the x axis is corrected by
adjusting the x coordinate (on the earth) of the NE control point, and
the distortion along the y axis is corrected by adjusting the y
coordinate (on the earth) of the SW control point.
In some cases perhaps the error is small enough not to have to worry
about, but it's probably a good idea to check.
-- Eric Johnson
Boulder, CO