WinTopo outputs the drawing at a scale of 1 pixel = 1 unit.

So if you raster image was 2000 pixels wide, for example, then the
drawing in ACAD would be 2000 units wide. If your drawing units in
ACAD are inches, then it would be 100's of feet wide.

You can work out the rescaling factor if you know the resolution at
which you scanned the image. For example, if you scanned at 200 dpi,
then you need to rescale by a factor of 1/200th (0.005) to get a
drawing of the same size.

You may also want to rescale to account for the scale at which the
original was drawn. In your case the scale of 3" = 1 foot is a
factor of 4.

Users of "WinTopo Pro" will be pleased to know that version 2.5 has
a new facility to automatically apply the appropriate scaling factor
to output the vector drawing at the correct size. WinTopo Pro 2.5
will be released very shortly. Any licensed user who would like to
upgrade straight away should e-mail the Support Team to request the
pre-release version.

From: The WinTopo Support Team

--- In wintopo@yahoogroups.com, "trikinimaster" <two@w...> wrote:
> I don't do this very often but was trying to import and convert a
> BMP scan of an old paper print (30 years) using version 1.1
> It did it and gave me a DXF which I opened in ACAD lt
> But that is a huge drawing showing 100's of ft by 100's of feet
> when I am trying to copy it from a 3" =1 ft drawing.
> No idea how to handle scale. can't get a full window, tried
> scaling and that reduces but won't resize the paper or move it.
> At a total loss <BG>
>
> TIA
>
> len