Novice: Contours from GIF

[James Cameron]

G'day,

I've scanned most carefully a portion of a topographic map, ensuring
that each pixel matches my resolution of five metres.  So my GIF file is
600 x 800 pixels, 3km by 4km.

I've been able to import it using r.in.gif and then adjust it's location
using r.support.  Displaying it actually worked too, with d.rast.

Questions:

1)  how do I make the display show only one portion of the area and
magnify it to show the original level of detail? Or better?

2)  how do I now digitise the GIF to produce a vector map of the
contours?  And a site map of some of the features?

--
James Cameron                                    (cameron at stl.dec.com)
Digital Equipment Corporation (Australia) Pty. Ltd. A.C.N. 000 446 800