Details Ticket 4249


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Serial Number 4249
Subject v.build.polylines: vertices are doubled at each node
Area grass6
Queue grass
Requestors tutey@o2.pl
Owner none
Status resolved
Last User Contact Fri Feb 23 16:34:22 2007 (2 yr ago)
Current Priority 30
Final Priority 70
Due No date assigned
Last Action Fri Feb 23 16:34:27 2007 (2 yr ago)
Created Wed Apr 5 14:07:10 2006 (2 yr ago)

Transaction History Ticket 4249


Wed, Apr 5 2006 14:07:10    Request created by guest  
Subject: v.build.polylines or v.clean: polylines created by v.build.polylines
are broken back into separate lines by v.clean

Platform: GNU/Linux/x86
grass obtained from: CVS
grass binary for platform: Compiled from Sources
GRASS Version: 2006-04-05

### There is a vector consisted of 3 lines connected with nodes:

$ v.build fafkulec
Building topology ...
3 primitives registered
Building areas:  100%
0 areas built
0 isles built
Attaching islands:
Attaching centroids:  100%
Topology was built.
Number of nodes     :   3
Number of primitives:   3
Number of points    :   0
Number of lines     :   3
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0



### I need to join lines into one:

v.build.polylines input=fafkulec output=fafkulec_poly

The number of lines in the binary map is 3

Polyline 0: start line = 3
The number of polylines in the output map is 1
Building topology ...
1 primitives registered
Building areas:  100%
0 areas built
0 isles built
Attaching islands:
Attaching centroids:  100%
Topology was built.
Number of nodes     :   1
Number of primitives:   1
Number of points    :   0
Number of lines     :   1
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0



### Fine. Only one line. But once I run v.clean on it, lines become separated
back. Somehow, points at which v.build.polylines joined the lines are taken for
errors by the v.clean:

$ v.clean input=fafkulec_poly output=fafkulec_poly_cl type=line error=fafkulec_poly_er
tool=break,rmdupl

+---------------------------------+---------------+
| Tool                            | Threshold     |
+---------------------------------+---------------+
| Break                            | 0.000000e+00 |
| Remove duplicates                | 0.000000e+00 |
+---------------------------------+---------------+
Copying vector lines ...
--------------------------------------------------
Rebuilding parts of topology ...
Building topology ...
1 primitives registered
Topology was built.
Number of nodes     :   1
Number of primitives:   1
Number of points    :   0
Number of lines     :   1
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   -
Number of isles     :   -
--------------------------------------------------
Tool: Break lines at intersections
Intersections:     2
--------------------------------------------------
Tool: Remove duplicates
Duplicates:     0
--------------------------------------------------
Rebuilding topology for output vector ...
Building topology ...
3 primitives registered
Building areas:  100%
0 areas built
0 isles built
Attaching islands:
Attaching centroids:  100%
Topology was built.
Number of nodes     :   3
Number of primitives:   3
Number of points    :   0
Number of lines     :   3
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0
--------------------------------------------------
Building topology for error vector ...
Building topology ...
2 primitives registered
Building areas:  100%
0 areas built
0 isles built
Attaching islands:
Attaching centroids:  100%
Topology was built.
Number of nodes     :   2
Number of primitives:   2
Number of points    :   2
Number of lines     :   0
Number of boundaries:   0
Number of centroids :   0
Number of areas     :   0
Number of isles     :   0


All the vectors mentioned above are in the location for download here:

http://www.biol.uni.wroc.pl/sieczka/udostepnione/grass/poly_clean.tar.bz2

Maciek
Wed, Jul 26 2006 18:23:35    User changed to tutey@o2.pl by msieczka  
Mon, Oct 2 2006 13:37:59    Subject changed to v.build.polylines: vertices are doubled at each node by msieczka  
Mon, Oct 2 2006 13:41:44    Mail sent by msieczka  
I have narrowed the problem down.

The bug is in v.build.polylines.

It produces doubled vertices at each input node, thus 'v.clean tool=break'
takes them for toplogy faults and breaks at those.

Workaround: run 'v.clean tool=prune thresh=0' on the v.bulid polylines output.
It will remove the bogus doubled vertices. Then 'v.clean tool=break' won't
break at those ex-nodes again.

Maciek
Fri, Feb 23 2007 16:34:22    Mail sent by mlanda  
Fixed in CVS.
Fri, Feb 23 2007 16:34:27    Status changed to resolved by mlanda  
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