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<p>Hi Giuseppe,</p>
<p>Thanks for confirming what I already suspected, and that
"geography" is not supported.</p>
<p>Maybe, as a first step to implementing this, just assuming the
globe is a perfect sphere instead of spheroid, would help in
easing implementing something like this for "geography", and
provide significant performance benefits as well. Since
'ST_ClusterDBSCAN' is already a non deterministic process, the
error of assuming the globe is a sphere is not particularily
relevant I think, but would allow you to run the clustering
process against a global data set.<br>
</p>
<p>Marco<br>
</p>
<div class="moz-cite-prefix">Op 21-12-2020 om 12:15 schreef Giuseppe
Broccolo:<br>
</div>
<blockquote type="cite"
cite="mid:CAFtuf8Br4vaGOTr=u23e6iccVFGgY9Wt20cpaFmkT8LsorzvMQ@mail.gmail.com">
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<div dir="ltr">
<div dir="ltr">Hi Marco,<br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Il giorno dom 20 dic 2020
alle ore 10:03 Marco Boeringa <<a
href="mailto:marco@boeringa.demon.nl"
moz-do-not-send="true">marco@boeringa.demon.nl</a>> ha
scritto:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
Reading through the PostGIS documentation, I noticed the <br>
"ST_ClusterDBSCAN" function takes a distance as one of the
inputs. Now <br>
the docs suggest the current algorithm only takes in
"geometry" type <br>
data. Is that true? Based on the distance input variable, it
would seem <br>
logical to have a "geography" variant as well, even if that
is a <br>
considerably slower variant considering the more complex
distance <br>
calculation.<br>
</blockquote>
<div><br>
</div>
<div>Yes, ST_ClusterDBSCAN takes just the geometry type in
input. This is because most of the algorithm</div>
<div>is implemented using utilities already existing in GEOS
for planar geometries.</div>
<div><br>
</div>
<div>Adding the support for the geography type would mean to
re-implement the algorithm specifically for</div>
<div>spherical objects, as you mentioned.</div>
<div><br>
</div>
<div>Regards,</div>
<div>Giuseppe.<br>
</div>
</div>
</div>
<br>
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