Details Ticket 4827


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Serial Number 4827
Subject Building topology for vector is incredibly slow
Area grass6
Queue grass
Requestors raffaele.morelli@apat.it
Owner none
Status open
Last User Contact Sat Jul 15 10:22:03 2006 (2 yr ago)
Current Priority 20
Final Priority 70
Due No date assigned
Last Action Sat Jul 15 10:22:03 2006 (2 yr ago)
Created Thu Jul 13 11:51:13 2006 (2 yr ago)

Transaction History Ticket 4827


Thu, Jul 13 2006 11:51:13    Request created by guest  
Subject: Building topology for vector is incredibly slow

Platform: Mac OSX
grass binary for platform: Downloaded precompiled Binaries
GRASS Version: 6.1.cvs_060624

Raffaele Morelli
I am working with several vector files from Italy I have imported from shape
files with v.in.ogr.
Those data comes with ISTAT census, so they are organized in several small polygons
for each town (called "sezioni").
I wanted to produce a global national vector with polygons representing towns
instead small areas inside towns, so I started running a shell script with all
the "v.extract -d .. .... " to dissolve boundaries from the same town. Finally
I came into a national vector map after patching the regional maps previously
obtained gatering towns from the same region.


After this I launched a v.clean to remove duplicates,small angles and break poligons.
The process runs normally but when it's time to build topology at the end of
v.clean the process is incredibly slow.
After 50 minutes is still running and the building areas progress is at 33%!!!
is this 'normal'?

I hope I exposed clearly enough to help you.
Thanx anyway
Sat, Jul 15 2006 10:22:03    Mail sent by hamish_nospam@yahoo.com  
Return-Path <hamish_nospam@yahoo.com>
Delivered-To grass-bugs@lists.intevation.de
Date Sat, 15 Jul 2006 20:21:54 +1200
From Hamish <hamish_nospam@yahoo.com>
To Request Tracker <grass-bugs@intevation.de>
Cc grass-dev@grass.itc.it
Subject Re: [GRASS-dev] [bug #4827] (grass) Building topology for vector is incredibly slow
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> this bug's URL: http://intevation.de/rt/webrt?serial_num=4827
> ---------------------------------------------------------------------
> 
> Subject: Building topology for vector is incredibly slow
> 
> Platform: Mac OSX
> grass binary for platform: Downloaded precompiled Binaries
> GRASS Version: 6.1.cvs_060624
> 
> Raffaele Morelli
> I am working with several vector files from Italy I have imported from
> shape files with v.in.ogr. Those data comes with ISTAT census, so they
> are organized in several small polygons for each town (called
> "sezioni"). I wanted to produce a global national vector with polygons
> representing towns instead small areas inside towns, so I started
> running a shell script with all the "v.extract -d .. .... " to
> dissolve boundaries from the same town. Finally I came into a national
> vector map after patching the regional maps previously obtained
> gatering towns from the same region.
> 
> 
> After this I launched a v.clean to remove duplicates,small angles and
> break poligons. The process runs normally but when it's time to build
> topology at the end of v.clean the process is incredibly slow. After
> 50 minutes is still running and the building areas progress is at
> 33%!!!
> 
> is this 'normal'?


run v.split before v.clean.


grass6/doc/vector/TODO says:

v.in.ogr
--------
It would be useful to split long boundaries to smaller
pieces. Otherwise cleaning process can become very slow because
bounding box of long boundaries can overlap large part of the map (for
example outline around all areas) and cleaning process is checking
intersection with all boundaries falling in the bounding box.


Hamish


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