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<p><font face="Arial">Azzurra,</font></p>
<p><font face="Arial"><br>
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<p><font face="Arial">Two other methods to try are:</font></p>
<p><font face="Arial"><br>
</font></p>
<p><font face="Arial">Point on surface</font></p>
<p><font face="Arial">Pole of inaccessibility <br>
</font></p>
<p><br>
</p>
<p>Both found in the Processing Toolbox</p>
<p><br>
</p>
<div class="moz-signature">
David<br>
<br>
<br>
</div>
<div class="moz-cite-prefix">On 1/12/2021 2:13 PM, Brent Wood wrote:<br>
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This may be a suitable approach, not specifically the ellipse
axis approach, but:</div>
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Vector -> Geometry tools -> Centroid</div>
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may do what you want, depending on exactly how QGIS calculates
the centroid...</div>
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<div class="BodyFragment">
<div class="PlainText">Brent Wood<br>
<br>
Principal Technician, Fisheries<br>
NIWA<br>
DDI: +64 (4) 3860529</div>
</div>
</div>
</div>
</div>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
face="Calibri, sans-serif" color="#000000"><b>From:</b>
Qgis-user <a class="moz-txt-link-rfc2396E" href="mailto:qgis-user-bounces@lists.osgeo.org"><qgis-user-bounces@lists.osgeo.org></a> on
behalf of Azzurra Lentini <a class="moz-txt-link-rfc2396E" href="mailto:azzurralentini@gmail.com"><azzurralentini@gmail.com></a><br>
<b>Sent:</b> Wednesday, January 13, 2021 08:04<br>
<b>To:</b> qgis-user <a class="moz-txt-link-rfc2396E" href="mailto:qgis-user@lists.osgeo.org"><qgis-user@lists.osgeo.org></a><br>
<b>Subject:</b> [Qgis-user] how to find center of polygons
and/or major and minor diameters</font>
<div> </div>
</div>
<div>
<div dir="ltr">
<div class="x_gmail_default"
style="font-family:tahoma,sans-serif"><font
style="background-color:rgb(255,255,255)"
color="#000000">Hi to all, any suggestion on how to
quickly draw <span style="font-family:inherit; white-space:pre-wrap">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.
</span></font></div>
<div class="x_gmail_default"
style="font-family:tahoma,sans-serif"><font
style="background-color:rgb(255,255,255)"
color="#000000"><span style="font-family:inherit; white-space:pre-wrap">
</span></font></div>
<div class="x_gmail_default"
style="font-family:tahoma,sans-serif"><font
style="background-color:rgb(255,255,255)"
color="#000000"><span style="font-family:inherit; white-space:pre-wrap">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)</span></font></div>
<div class="x_gmail_default"
style="font-family:tahoma,sans-serif"><font
style="background-color:rgb(255,255,255)"
color="#000000"><span style="font-family:inherit; white-space:pre-wrap">
</span></font></div>
<div class="x_gmail_default"
style="font-family:tahoma,sans-serif"><font
style="background-color:rgb(255,255,255)"
color="#000000"><span style="font-family:inherit; white-space:pre-wrap">Thanks, Azzurra
</span></font></div>
<div class="x_gmail_default"
style="font-family:tahoma,sans-serif"><font
style="background-color:rgb(255,255,255)"
color="#000000"><span style="font-family:inherit; white-space:pre-wrap">
</span></font></div>
<font style="background-color:rgb(255,255,255)"
color="#000000">-- </font><br>
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">Lecturer GIS University "Roma
Tre"<br>
</div>
<div dir="ltr">Consultant Environmental Risk
Prevention and Hydrogeology<br>
AZZURRA LENTINI </div>
<div dir="ltr">++++++++++++++++++++++++++<br>
Italy Mobile Tel.: **(39) 338 24 40 676<br>
++++++++++++++++++++++++++<br>
SKYPE azzurrahydro<br>
++++++++++++++++++++++++++</div>
<div>
<p class="x_MsoNormal"
style="margin-bottom:0.0001pt;
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background-position:initial;
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line-height:normal">
<b><u><span style="font-size:12pt;
font-family:Arial,sans-serif;
color:blue"><a
href="mailto:azzurralentini@gmail.com"
target="_blank"
style="color:rgb(17,85,204)"
moz-do-not-send="true">azzurralentini@gmail.com</a></span></u></b></p>
<p class="x_MsoNormal"
style="margin-bottom:0.0001pt;
line-height:normal;
background-image:initial;
background-position:initial;
background-repeat:initial">
<b><u><span style="font-size:12pt;
font-family:Arial,sans-serif;
color:blue"><a
href="mailto:azzurra.lentini@uniroma3.it"
target="_blank"
style="color:rgb(17,85,204)"
moz-do-not-send="true">azzurra.lentini@uniroma3.it</a> </span></u></b><b><u><span
style="font-size:12pt;
font-family:Arial,sans-serif;
color:blue"> </span></u></b><br>
</p>
</div>
<div dir="ltr">++++++++++++++++++++++++++<br>
*Par respect pour l'environnement,*<br>
<br>
*n'imprimez ce mail qu'en cas d'absolue
nécessité*</div>
</div>
<div dir="ltr"> <br>
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src="https://www.niwa.co.nz/static/niwa-2018-horizontal-180.png"
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</td>
<td>
<span>Brent Wood<br>
<font color="#1793d2">Principal Technician - GIS and
Spatial Data Management</font><br>
<font color="#1793d2">Programme Leader - Environmental
Information Delivery</font><br>
+64-4-386-0529 | <br>
National Institute of Water & Atmospheric Research
Ltd (NIWA)<br>
301 Evans Bay Parade Hataitai Wellington New Zealand<br>
<b>Connect with NIWA:</b> <a
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