[GRASSLIST:2333] Re: Removing a section of a raster map

[Michel Wurtz]

Rich Shepard wrote:

>   When the raster image displays in the monitor, it is centered
> horizontally and has space on either side. Why it disappeared when I invoked
> v.digit I cannot say. For that matter, as I was watching the window with the
> v.digit setup I cannot even tell you just when the monitor changed.

You must tell v.digit to use a background :

v.digit start with a rectangualr area showing the boundaries of the region
you just defined for your new vector file (you MUST have filled scale, north,
south, east and west fields).

then use the 'C' (customize) command, then 'B' (use a backdrop CELL), and
answer y to the message :

 Do you want to automatically redraw backdrop on re-window? (y/n) [y]

after that q (quit the Customiez menu) and D for digitizing (by default,
you should digitize area, if not, use 't' for type change)


After closing your rectangle (it should be automatic if the 5th point
is close enough to the first), you have to label your polygon ('L' command
after quiting digitize). choose 'a' (area label)
No name is needed, and answer 1 to the question :

 Enter Category Number (0 to quit):[0] 1

chose a point in the middle of your rectangle, then select the line around and
accept it.  you should see now a .1 and the boundary in orange.

quit v.digit, and verify if everyting is good with d.rast + d.vect
then v.support, v.to.rast and r.mapcalc should work

If you need it, I can sent you some snapshoot of the v.digit's screens
(but not on the mailing list ;-)

--
Michel WURTZ - DIG - Maison de la télédétection
               500, rue J.F. Breton
               34093 MONTPELLIER Cedex 5