[Qgis-user] how to find center of polygons and/or major and minor diameters

David Greenewalt dlg at sover.net
Tue Jan 12 11:24:24 PST 2021


Azzurra,


Two other methods to try are:


Point on surface

Pole of inaccessibility


Both found in the Processing Toolbox


David


On 1/12/2021 2:13 PM, Brent Wood wrote:
> This may be a suitable approach, not specifically the ellipse axis 
> approach, but:
>
>
> Vector -> Geometry tools -> Centroid
>
> may do what you want, depending on exactly how QGIS calculates the 
> centroid...
>
>
>
> Brent Wood
>
> Principal Technician, Fisheries
> NIWA
> DDI:  +64 (4) 3860529
>
> ------------------------------------------------------------------------
> *From:* Qgis-user <qgis-user-bounces at lists.osgeo.org> on behalf of 
> Azzurra Lentini <azzurralentini at gmail.com>
> *Sent:* Wednesday, January 13, 2021 08:04
> *To:* qgis-user <qgis-user at lists.osgeo.org>
> *Subject:* [Qgis-user] how to find center of polygons and/or major and 
> minor diameters
> Hi to all, any suggestion on how to quickly draw the minor and major 
> diameters of different polygons? I have a shapefile of polygons: some 
> of the polygons are ellipses and others are similar to ellipses but 
> not regular.
> My aim is to find the center of these polygons (In this aim I was 
> thinking to draw the 2 diameters and to use the intersection of these 
> diameters as a center point of the polygon)
> Thanks, Azzurra
> -- 
> Lecturer GIS University "Roma Tre"
> Consultant Environmental Risk Prevention and Hydrogeology
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>
>
>
> <https://www.niwa.co.nz> 	Brent Wood
> Principal Technician - GIS and Spatial Data Management
> Programme Leader - Environmental Information Delivery
> +64-4-386-0529 |
> National Institute of Water & Atmospheric Research Ltd (NIWA)
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