[Qgis-user] Ho to intersect layers with some conditions

[Faadil Khan]

HI, Can you please remove me from this user list.

 

Regards,

 

Faadil Khan

Tel: 011 675 5111

Fax: 011 675 7018

 <http://www.shama.co.za> www.shama.co.za

 



 

From: qgis-user-bounces at lists.osgeo.org
[mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of G. Allegri
Sent: 11 April 2013 09:53 AM
To: Levy Vincent
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] Ho to intersect layers with some conditions

 

I fear it isn't possible to do it in one single step. If I had to do it in a
rush I would:

 

 - add a column to the grid layer and populate it with the square area. Your
squares are fixed, so you can populate it manually, otherwise the field
calculator could be used to do it

 - do an intersect between you polygon and the grid (Vector ->
Geoprocessing)

 - add another column to the intersection result, and populate it again with
the area, using the Filed Calculator.

 - AT this point you will have the original area and the new area. With
Field Calculator populate a third column with the new area / original area
ratio (x 100 if you want the precentage).

 - Select the squares where the percentega is over 90.

 

How to obtain the unclipped, original, squares? You can do a spatial join
between the original grid, and the selected squares (above 90) from the
intersection result.

 

Giovanni

2013/4/11 Levy Vincent <v.levy at cbnbl.org>

Hello,

 

I have a layer with a big polygon and another layer which is a grid (made of
squares 10X10m). The grid is larger than the big polygon and cover it
entirely. 

I want to keep only the squares of the grid contained in the polygon. I know
how to intersect my two layers  to select all the squares of the grid inside
my “big polygon”.

The problem is on the border : I would like to select only the squares which
90% of their surface is contained in the big polygon.

Is there any plug-in or another solution to do it easily?

I hope somebody could help me, thank you for your answer,

 

Vincent LEVY

Chargé de mission scientifique

Conservatoire botanique national de Bailleul

Antenne Picardie

13 allée de la Pépinière

Centre Oasis

80044 AMIENS CEDEX 1

Tél./Fax: 03 22 89 69 78

v.levy at cbnbl.org

 

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-- 
Giovanni Allegri
http://about.me/giovanniallegri
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus 

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