Labeling Areas

[Shawn Francis]

Adalberto:

>
>	I'm trying to label some areas that I've imported from AutoCad
>primarily for generate a half-dozen masks.
>
>	I've drawn some rectangles (closed polylines), export to dxf and import
>them to Grass (v.in.dxf). When I ran v.support, Grass only recognizes
>the rectangles as lines with one node point (the same occurs if those
>rectangles were exported as several singular lines from AutoCad -- we
>can achieve this by 'exploding' polylines under AutoCad).
>
>	Then I tried to label these areas under v.digit. The labeling
>procedures only accept attach labels to each line: I start labeling,
>choose one line and it highlights the four segments of the rectangle
>(with a tiny coloured node at upper&leftmost corner), and accept the
>label.
>
>	If I try to label the area inside that four 'walls', it fails. I
>started area labeling, put category number, clicked a point near the
>centre of the rectangle (better saying: near the centre of the area
>defined by that four segments & one node line), selected the line itself
>when prompted for "Select a Boundary line:" , and the prompt then says
>there is not a line where I clicked (and I tried several points to
>click...).
>
>	Do you know what's going wrong?
>
>	Many thanks,
>
>	Adalberto da Silva
>	Instituto Astronomico e Geofisico - USP
>	Sao Paulo - SP
>	Brasil
>	adalbert at iag.usp.br

        GRASS is kind of funny in that it handles LINES and AREA EDGES
separately.  LINES are for the representation of linear features while AREA
EDGES, as the name suggests, are used to form polygon boundaries.  To get
your DXF lines into polygons, you will have to "toggle line type" in the
EDIT menu of v.digit.  Then you will be able to create a polygon.  This can
also be done by text editing the vector ascii file, but for such a small
file the v.digit option is probably faster.  Hope this helps.

Shawn Francis,
Forest Ecologist and GIS Analyst

Applied Ecosystem Management
100-114 Galena Road
Whitehorse, Yukon  Y1A 2W6
tel/fax (867) 393-3793
aem at yknet.yk.ca