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 <[email protected]> on behalf of Azzurra Lentini <[email protected]> Sent: Wednesday, January 13, 2021 08:04 To: qgis-user <[email protected]> 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 AZZURRA LENTINI ++++++++++++++++++++++++++ Italy Mobile Tel.: **(39) 338 24 40 676 ++++++++++++++++++++++++++ SKYPE azzurrahydro ++++++++++++++++++++++++++ [email protected]<mailto:[email protected]> [email protected]<mailto:[email protected]> ++++++++++++++++++++++++++ *Par respect pour l'environnement,* *n'imprimez ce mail qu'en cas d'absolue nécessité* [https://www.niwa.co.nz/static/niwa-2018-horizontal-180.png]<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) 301 Evans Bay Parade Hataitai Wellington New Zealand Connect with NIWA: niwa.co.nz<https://www.niwa.co.nz> Facebook<https://www.facebook.com/nzniwa> LinkedIn<https://www.linkedin.com/company/niwa> Twitter<https://twitter.com/niwa_nz> Instagram<https://www.instagram.com/niwa_science> To ensure compliance with legal requirements and to maintain cyber security standards, NIWA's IT systems are subject to ongoing monitoring, activity logging and auditing. This monitoring and auditing service may be provided by third parties. Such third parties can access information transmitted to, processed by and stored on NIWA's IT systems
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