[GRASSLIST:807] Re: Vector to Raster Lakes

[H Bowman]

> > v.line2area
> > d.vect.area fill=blue
>
> I tried to use this method.  The problem I am running into is that
> when I run v.support, it is telling me the line areas are not enclose.
>  I think that it means that the lines bounding the lakes have not been
>  closed properly.  When I use the v.line2area and the d.vect.area, the
>  d.mon goes completely white, no trace of the maps.
>
> Any other ideas?


I had to deal with this same problem two days ago, and won. It was messy
so I can't tell you the exact procedure, but here are some hints...

The v.support error either means a complete circuit hasn't been made or
there is a dangling line pointing inwards from the edge of the area.

You can test which it is with v.digit.

Go into the Toolbox menu and try "o" to find open lines or "i" to show
completed islands. 

Use "!" to redraw the screen or Window->"C" to blank it and get rid of
any yellow lines between these, as they both highlight to yellow.

If the line isn't closed, you should see green dots for the end points.
Snap them together with Edit->"s" snap.

If you can't find a break but it still won't register as an area, you
may have a line dangling inwards off a node. Fix by zooming and
Edit->"r" in v.digit or with v.spag.

In coastline files, I often find open ends either side of a river mouth.
Snapping these shut automatically will sometimes leave dangling lines.

You'll need to label your areas once you have them to be able to display
with d.vect.area. Use v.alabel or in v.digit with Label->"a".

other things to try:
v.build.polylines type=area
v.spag thresh=xx   <- this command strips dangling lines shorter than thresh
or
v.support -s thresh=xx


good luck,
Hamish