[Qgis-user] Fix Geometries

Fri May 24 09:15:15 PDT 2019

Bonjour Alain,

I read the document and it's useful.   IMHO, this should be included in 
the QGIS documentation in the future.  Under QGIS 3.6.2, I used the 
plugin but I had to fix one problem at a time because of stability 
issues.  I did not make a bug report because one was already active.  I 
may be able to give you access to my shape file if you are interested in 
trouble shooting.  I would need to ask first because I do not own this 
database but I am confident I could obtain permission.  Send me a 
private email if you need more info.

Bonne journée!

Nicolas Cadieux

On 2019-05-24 3:20 a.m., FERRATON Alain (Chef de groupe) - 
SG/SPSSI/CPII/DOO/ET wrote:
> Hi,
>
> We published a document in early 2018 on geometry fixes.
> This document should be revised, but may provide some elements.
> (For example, geometry checker is now more stable under QGIS 3)
>
> It is open for comments...
> We have in our projects to produce a more user-friendly version
>
> see : 
> http://geoinformations.metier.e2.rie.gouv.fr/spip.php?page=article&id_article=3522&id_rubrique=712
> see the document at the bottom of the page
>
> Regards,
> Alain
>
> FERRATON Alain
> Ministère de la Transition écologique et solidaire (MTES)
> SG/SPSSI/CPII/DOO
> Chef du groupe Expertise Technique
> 02.40.12.84.08
>
> Le 23/05/2019 à 13:07, > Richard McDonnell (par Internet, dépôt 
> qgis-user-bounces at lists.osgeo.org) a écrit :
>> Hi Finbar,
>> One other solution would be to use a double buffer, as in a positive 
>> buffer something like 0.001, followed by a negative buffer of -0.001.
>> The issue you are facing is common, as most flood polygons are 
>> derived from raster's and you can get a lot of self-intersections. 
>> The double buffer is in my experience the handiest method of solving 
>> the issue. Also by using such a small buffer, even a single buffer, 
>> will make little difference, to a house being in or out of a flood 
>> zone, when taking into account the, resolutions of the polygon datasets.
>> Hope this helps,
>>
>> Regards,
>>
>> Richard.
>>
>> -- 
>>
>>
>> Richard McDonnell
>> GIS Specialist | FRM Data Management
>>
>>
>> Email:  richard.mcdonnell at opw.ie
>>
>>
>> Phone:  + 353 (0) 1 647 6543
>>
>>
>> Mobile:  +353 (0) 87 688 5964
>>
>> The Office of Public Works
>> 52 St. Stephen's Green
>> Dublin 2 ~ D02 DR67
>>
>>
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: Qgis-user <qgis-user-bounces at lists.osgeo.org> On Behalf Of 
>> GILLEN Finbar
>> Sent: 22 May 2019 11:40
>> To: qgis-user at lists.osgeo.org
>> Subject: Re: [Qgis-user] Fix Geometries
>>
>> Thanks for all the responses on this... I am going to try the Check 
>> Validity plugin ('QGIS' method) as a starter within QGIS 3.2. I am 
>> using a fairly detailed flood polygon so accuracy is key. I will let 
>> you know how I get on.
>>
>> Thanks again,
>> Finbar
>>
>> -----Original Message-----
>> From: Qgis-user <qgis-user-bounces at lists.osgeo.org> On Behalf Of 
>> Nicolas Cadieux
>> Sent: 21 May 2019 23:02
>> To: qgis-user at lists.osgeo.org
>> Subject: Re: [Qgis-user] Fix Geometries
>>
>> Hi,
>>
>> The Geometry Checker plugin will add a the 'Check Geometries' option 
>> in the vector menu.  It is very unstable with the current version of 
>> QGIS. If you get it to run, it should solve most problems.  I get it 
>> to run when I only select one test at a time.
>>
>> The most predictable tool is the vector/geometry tools/Check validity 
>> using the 'QGIS' Method (not GEOS).  That should fix your file.  
>> There is a 'remove duplicate vertices' and 'delete duplicate 
>> geometries' in processing.  Your problem could also be caused by a 
>> module not working with multipart objects.  Go to vector/Geometry 
>> tools/Multiparts to singleparts.
>>
>> If your lines don't touch,   try the 'snap Geometries to layer ' in 
>> processing.
>>
>> Nicolas
>>
>> On 2019-05-21 2:54 a.m., Mithoefer wrote:
>>> Hi Finnbar,
>>>
>>> What plugin are you talking about and what QGIS version do you use?
>>> You have a number of tools to check geometries. Try "Topology checker"
>>> or "Geometry checker" to see where the problems are (invalid
>>> geometries). Geometry checker is also able to fix some issues. Maybe
>>> thats the one you use.
>>>
>>> Anotehr option is GRASS GIS. Have you ever worked wit GRASS GIS? You
>>> can create a GRASS database and import your polygons. GRASS GIS uses a
>>> topolgical data model and is quite powerful in establishing a desent
>>> data model with snapping options and clean functions. You can also try
>>> GRASS tools from the processing framework like build polygons or clean.
>>>
>>> Regards
>>> Klaus
>>>
>>> Am 20.05.19 um 11:31 schrieb GILLEN Finbar:
>>>> Hi All,
>>>>
>>>> I have a few polygon layers where anytime I go to use them I have to
>>>> use the fix geometries plugin so that invalid geometries are fixed.
>>>>
>>>> When I save the output from the fixed geometries plugin and add it in
>>>> a new project the same issues appears where I can’t use it accurately
>>>> to do a Select or Join by Location because some of the geometries are
>>>> still seen as invalid even though they have been ‘fixed’.
>>>>
>>>> Is there anyway solution to this or do I have to keep using the fix
>>>> geometries plugin anytime I use the polygons for analysis?
>>>>
>>>> Regards
>>>>
>>>> Finbar
>>>>
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>> business in Northern Ireland, AXA Insurance dac is authorised by the 
>> Central Bank of Ireland and subject to limited regulation by the 
>> Financial Conduct Authority. Details about the extent of our 
>> regulation by the Financial Conduct Authority are available from us 
>> on request. AXA Insurance dac is a private company limited by shares, 
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