Polygons into GRASS

[Mark Gregory]

GRASS users--

I have a digitized representation of a set of polygons, such as a soils map.
Unfortunately, the map is divided into a serial of data sets where each data
set contains complete polygons for all areas of that same value.  That is,
data set number 1 contains complete polygons for all areas designated as soil
type 1; data set number 2 contains complete polygons for all areas designated
as soil type 2; and so on.  Also, none of the polygons have attribute or label
points associated with them (but I know what their label should be based upon
the data set the polygon is in).

I can import the separate files into GRASS and make separate dig files.  My 
first question:

1.  Is there any way to bulk label polygons within GRASS (much like bulk 
labeling of lines within v.digit)?  If there is no way to automatically label
a polygon, is there a way to generate a centroid within a GRASS polygon?

If I can efficiently label the polygons by data set, I then intend to v.patch
the various dig files together.  My next question then:

2.  Can I eliminate the overlap between the edges of two adjoining polygons?
That is, can I convert the complete polygons which result in the storage of
duplicate coordinates between adjoining polygons into a vector representation
where adjoining polygons both utilize the same segment/vector to construct each
polygon?  I tried the GRASS4.0 version of v.spag with threshold=0 and while it
works for part of the polygon, it seems to get 'hung in a loop' in other parts
of the data set.

Any thoughts on either of these two problems would be greatly appreciated.

Thanks,

Mark Gregory                     mg at soil.agr.okstate.edu
Oklahoma State University        (405) 744-6417