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<font size="+1"><font face="Arial">This can be achieved using the
PostGIS function ST_MinimumBoundingCircle(). If you can import
your subplots point layer into a PostGIS database, then
(assuming the points have an attribute "subplot_id", and
geometry column "the_geom") you could do something like:<br>
<br>
</font></font><font size="+1"><tt>SELECT s.subplot_id,
ST_MinimumBoundingCircle(ST_Collect(s.the</tt><tt>_geom)</tt><tt>)
as the_geom</tt><tt><br>
</tt><tt> FROM subplots AS s</tt><tt><br>
</tt><tt> GROUP BY s.subplot_id;</tt></font><font size="+1"><font
face="Arial"><br>
<br>
(Based on the example from
<a class="moz-txt-link-freetext" href="http://postgis.net/docs/ST_MinimumBoundingCircle.html">http://postgis.net/docs/ST_MinimumBoundingCircle.html</a>)<br>
<br>
<br>
I would also point out that there's a concept "Standard
Deviational Ellipse" for encircling points by an ellipse at a
certain stdev distance from the "center of gravity" of the
points. If this is of interest, you can implement it in
GRASS-GIS with the </font></font><font size="+1"><tt>v.ellipse</tt></font><font
size="+1"><font face="Arial"> addon. <br>
<br>
</font></font><br>
<div class="moz-cite-prefix">On 08/07/2016 16:49, Tina Cormier
wrote:<br>
</div>
<blockquote
cite="mid:CAFfx7689kt_FnT5xO+XMmV4u-beic1iGh9q_St+Zkg1Fbf=tQw@mail.gmail.com"
type="cite">
<div dir="ltr">Hi all,
<div><br>
</div>
<div>Looking for help aggregating some field data subplots to
the plot level. In the attached screenshot, you can see
clusters of 4 points (4 subplots = 1 plot). I'd like to create
a circle around each cluster that is the smallest circle that
would encompass all 4 points. Sort of like a convex hull, but
a circle (convex hull, in this case, would give me a
triangle). Is there a tool or a series of steps to accomplish
this without doing it manually? In the attribute table, I have
a unique ID for each plot/cluster. So for each plot ID (in
this case, consisting of 4 subplots), I'd like to build a
circle around all of the subplots.</div>
<div><br>
</div>
<div>I should also mention that it's not always 4 points
(subplots), and they aren't always covering the same size area
on the ground.</div>
<div><br>
</div>
<div>I have QGIS 2.14.2 as well as one of the nightly builds
from a few weeks ago (can download the newest one if
necessary).</div>
<div><br>
</div>
<div>Thanks in advance for any ideas/insights! Google has not
helped me so much yet with this one!</div>
<div>Tina</div>
<div><br>
</div>
<div><br>
</div>
<div><img src="cid:part1.B783CD59.C8CC032B@arava.co.il"
alt="Inline image 2" height="496" width="544"><br>
</div>
</div>
<br>
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<br>
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Micha Silver
Arava Drainage Authority
+972-523-665918</pre>
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