[GRASS-user] generate polygon from lines

[Craig Feuerherdt]

I have a vector layer that contains lines which define a polygon.
I have attempted to build a polygon from the layer but have not had much
luck.

I have used v.clean input=bnd output=bndc tool=snap thres=0.0001 to snap any
small dangles together (my data is in lats/longs) which output the
following;

+---------------------------------+---------------+
| Tool                            | Threshold     |
+---------------------------------+---------------+
| Snap vertices                    | 1.000000e-04 |
+---------------------------------+---------------+
Copying vector lines ...
--------------------------------------------------
Rebuilding parts of topology ...
Building topology ...
234 primitives registered
Topology was built.
Number of nodes     :   238
Number of primitives:   234
Number of points    :   0
Number of lines     :   234
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   -
Number of isles     :   -
--------------------------------------------------
Tool: Snap line to vertex in threshold
All vertices:  2140
Registered points (unique coordinates):  1910
Nodes marked as anchor     :  1837
Nodes marked to be snapped :    79
Snapped vertices :    88
New vertices     :     3
--------------------------------------------------
Rebuilding topology for output vector ...
Building topology ...
234 primitives registered
Building areas:  100%
0 areas built
0 isles built
Attaching islands:
Attaching centroids:  100%
Topology was built.
Number of nodes     :   235
Number of primitives:   234
Number of points    :   0
Number of lines     :   234
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0

I then used v.build map=bndc error=err option=build --overwrite which output
the following;

Building topology ...
234 primitives registered
Building areas:  100%
0 areas built
0 isles built
Attaching islands:
Attaching centroids:  100%
Topology was built.
Number of nodes     :   235
Number of primitives:   234
Number of points    :   0
Number of lines     :   234
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0
WARNING: The vector 'err' already exists and will be overwritten.
Building topology ...
0 primitives registered
0 areas built
0 isles built
Attaching islands:
Attaching centroids: Topology was built.
Number of nodes     :   0
Number of primitives:   0
Number of points    :   0
Number of lines     :   0
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0

Obviously there were no polygons created.
Regardless of the combinations I try (ie v.clean with the break option,
followed by v.clean with the snap option) I am unable to create a polygon.
I have added the shapefile into QGIS and physically viewed the line to check
if there are any gaps - which there aren't.

What am I missing?

I am using grass 6.0.1 on gentoo.

Craig
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