[GRASSLIST:8055] Re: V.digit (GRASS): Layer disapears, using QGIS as front end

[Stephan Holl]

Hello Dave, 

On Wed, 24 Aug 2005 09:17:52 -0400 Dave Sampson <gis at watersheds.ca>
wrote:

> Hey GRASS/QGIS folks.
> 
> I have a base vector layer for a lake that I wish to digitize over.
> 
> When I use v.digit and create a new layer, my display blanks, hiding
> the lake layer. The VIEW does not change extents as I can display the
> new dumby vector over the old one after I SAVE AND EXIT. However its
> hard to line up a land feature to the shoreline without seeing the
> shoreline while digitizing.
> 
> My work around is to make a dumby vector in GRASSA and then digitize
> in QGIS. Which brings up a second issue. If I delete the dumby vector
> in QGIS before making a new one, the vector file becomes currupt for
> both QGIS and GRASS. So you start with one dumby vector in GRASS,
> create a new less obtrusive dumby vector in QGIS and delete the old
> dumby GRASS vector before you start digitizing. To say the least, a
> few extra steps that would be nice to avoid. This would be a major
> drawback to using GRASS/QGIS in a production digitizing scenario.
> 
> How do I use GRASS to digitize a new layer over an existing one. Do I 
> need to provide more info to this list?

To digitazie from a backdrop-map you could use the following command:

in GRASS:
d.mon x0
v.digit -n <mynewvectormap>  -bgcmd='d.rast backdropmap;d.vect
oldvector'

Perhaps this is what you need?

Cheers
	Stephan

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