[GRASS5] [bug #858] (grass) v.support/v.build bug identified!

GRASS GRASS developer
1

this bug's URL: http://intevation.de/rt/webrt?serial_num=858
-------------------------------------------------------------------------

Subject: v.support/v.build bug identified!

grass downloaded at: CVS Server, Germany

The v.support/v.build bug with causes the PNT_TO_AREA failed warnings
seems to be identified.

A micro-demo-location to reproduce the problem is available at
http://mpa.itc.it/markus/tmp/

The location contains to sample vector maps "good" and "bad",
each with two polygons only:

GRASS:~/grassdata/patdemo > l
total 12
drwxr-xr-x 2 neteler ssi 4096 Nov 26 19:49 PERMANENT
drwxr-xr-x 2 neteler ssi 4096 Nov 26 19:52 rawdata
drwxrwxrwx 7 neteler ssi 4096 Nov 26 19:55 vector

In rawdata are the ARC-ASCII vector files and two import
scripts:

GRASS:~/grassdata/patdemo > ls -la rawdata
total 40
drwxr-xr-x 2 neteler ssi 4096 Nov 26 19:52 .
drwxr-xr-x 5 neteler ssi 4096 Nov 26 19:51 ..
-rw-r--r-- 1 neteler ssi 35 Nov 26 19:51 BadExample.dat
-rw-r--r-- 1 neteler ssi 67 Nov 26 19:51 BadExample.pnt
-rw-r--r-- 1 neteler ssi 273 Nov 26 19:51 BadExample.pol
-rw-r--r-- 1 neteler ssi 35 Nov 26 19:51 GoodExample.dat
-rw-r--r-- 1 neteler ssi 67 Nov 26 19:51 GoodExample.pnt
-rw-r--r-- 1 neteler ssi 273 Nov 26 19:51 GoodExample.pol
-rwxr-xr-x 1 neteler ssi 154 Nov 26 19:52 import.BadExample.sh
-rwxr-xr-x 1 neteler ssi 159 Nov 26 19:52 import.GoodExample.sh

Now the GRASS bug: v.support writes
PNT_TO_AREA failed: (1681015.000000, 5118635.000000) (Category 694020)
PNT_TO_AREA failed: (1680445.000000, 5118795.000000) (Category 54014)

when two or more polygons have the same starting point (the "bad" map).
The identical "good" map with rotated nodes runs well.

That may be the key to understand all the E00 and SHAPE problems
which are regularly reported.

Thanks to Lorenzo Potrich (ITC-irst) for identifying this problem.

Please someone may fix this severe problem...

Markus Neteler

-------------------------------------------- Managed by Request Tracker

2

On Mon 26. November 2001 20:03, Request Tracker wrote:

I'm not sure if this is realy v.build bug. v.build is designed for building
topology from clean linework. Two polygons with duplicated boundary is
not clean. Unfortunately cleaning module v.spag is only reliable for '-i'
flag.
My solution for those who have imported files with clean topology
(export from ArcInfo for example, not ArcView) and good computer
(time consuming method):

v.drop input=bad output=bad.drop
cp vector/dig_att/bad vector/dig_att/bad.drop # sorry, no support for dig_att files in v.drop
v.support map=bad.drop
v.spag -i map=bad.drop
v.build.polylines -c -o input=bad.drop output=bad.ok type=area

Result:
Number of lines: 3
Number of nodes: 2
Number of areas: 2
Number of isles: 1
Number of atts : 2
Number of unattached atts : 0
Snapped lines : 0

This should reduce size of the vector (areas) to one half also.

v.drop: http://www.raz-dva.cz/krakonos/v.drop.tar

Radim

this bug's URL: http://intevation.de/rt/webrt?serial_num=858
-------------------------------------------------------------------------

Subject: v.support/v.build bug identified!

grass downloaded at: CVS Server, Germany

The v.support/v.build bug with causes the PNT_TO_AREA failed warnings
seems to be identified.

A micro-demo-location to reproduce the problem is available at
http://mpa.itc.it/markus/tmp/

The location contains to sample vector maps "good" and "bad",
each with two polygons only:

GRASS:~/grassdata/patdemo > l
total 12
drwxr-xr-x 2 neteler ssi 4096 Nov 26 19:49 PERMANENT
drwxr-xr-x 2 neteler ssi 4096 Nov 26 19:52 rawdata
drwxrwxrwx 7 neteler ssi 4096 Nov 26 19:55 vector

In rawdata are the ARC-ASCII vector files and two import
scripts:

GRASS:~/grassdata/patdemo > ls -la rawdata
total 40
drwxr-xr-x 2 neteler ssi 4096 Nov 26 19:52 .
drwxr-xr-x 5 neteler ssi 4096 Nov 26 19:51 ..
-rw-r--r-- 1 neteler ssi 35 Nov 26 19:51 BadExample.dat
-rw-r--r-- 1 neteler ssi 67 Nov 26 19:51 BadExample.pnt
-rw-r--r-- 1 neteler ssi 273 Nov 26 19:51 BadExample.pol
-rw-r--r-- 1 neteler ssi 35 Nov 26 19:51 GoodExample.dat
-rw-r--r-- 1 neteler ssi 67 Nov 26 19:51 GoodExample.pnt
-rw-r--r-- 1 neteler ssi 273 Nov 26 19:51 GoodExample.pol
-rwxr-xr-x 1 neteler ssi 154 Nov 26 19:52
import.BadExample.sh -rwxr-xr-x 1 neteler ssi 159 Nov 26
19:52 import.GoodExample.sh

Now the GRASS bug: v.support writes
PNT_TO_AREA failed: (1681015.000000, 5118635.000000) (Category 694020)
PNT_TO_AREA failed: (1680445.000000, 5118795.000000) (Category 54014)

when two or more polygons have the same starting point (the "bad" map).
The identical "good" map with rotated nodes runs well.

That may be the key to understand all the E00 and SHAPE problems
which are regularly reported.

Thanks to Lorenzo Potrich (ITC-irst) for identifying this problem.

Please someone may fix this severe problem...

Markus Neteler

-------------------------------------------- Managed by Request Tracker
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