[postgis-users] Is there a simple way to generate polygon from random points?

Regina Obe lr at pcorp.us
Fri Sep 8 07:07:53 PDT 2023



There are some examples in the manual.  There is a ST_ConcaveHull function and an ST_AlphaShape.  Both do essentially the same thing but use different engines.


Part of postgis extension, uses GEOS under the hood



Part of postgis_sfcgal – uses CGAL under the hood.

The ST_AlphaShape one is only available if you have postgis_sfcgal extension installed.





To Barend,


Thanks for your consideration of our time, but I think it’s better for people to not fear asking questions and worry the question they are asking is something they should have looked up in the manual.  I’d rather they ask, and we point them to the section of the manual where it is detailed.


This mailing list isn’t so crowded that we can’t simply ignore questions we’d rather not bother answering.  David asks very useful questions that I think a lot of people could benefit from searching our mail list archives for and that to me is a great contribution, so please don’t discourage him.







From: postgis-users <postgis-users-bounces at lists.osgeo.org> On Behalf Of Kobben, Barend (UT-ITC) via postgis-users
Sent: Friday, September 8, 2023 9:57 AM
To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
Cc: Kobben, Barend (UT-ITC) <b.j.kobben at utwente.nl>
Subject: Re: [postgis-users] Is there a simple way to generate polygon from random points?


Really Shaozhong Shi (David)...? After all these years of open questions without any focus you cannot even lookup the functions the respondent mentioned yourself, in the excellent PostGIS  manual...?


Please have some consideration for the people putting in their time to help others. RTFM.


Barend Köbben



On 08/09/2023, 15:37, "postgis-users" <postgis-users-bounces at lists.osgeo.org <mailto:postgis-users-bounces at lists.osgeo.org> > wrote:

Is there a sample script?



On Friday, 8 September 2023, Erik Wienhold <ewie at ewie.name <mailto:ewie at ewie.name> > wrote:

On 08/09/2023 13:34 CEST Shaozhong SHI <shishaozhong at gmail.com <mailto:shishaozhong at gmail.com> > wrote:

> Is there a simple way to generate polygon from random points?

Compute the convex or concave hull or an alpha shape.  PostGIS provides
functions for all three of them.


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