[postgis-users] generate a geometry column of random point, line and polygon

[Regina Obe]

David,

 

For this are you needing to generate random points from a line or polygon or are you trying to generate random polygons, lines, and points?

 

If you need to generate random points from a polygon:

 

Use ST_GeneratePoints:  https://postgis.net/docs/en/ST_GeneratePoints.html

Note there is a option seed argument, that will give you the same exact answer if you give it the same seed, but without that the generated points will be different each time.

 

As I recall, ST_GeneratePoints only works with areals so won’t work with a line, however you can buffer a line very thinly to do the same. Use a flat buffer:

 

https://postgis.net/docs/en/ST_Buffer.html

 

SELECT ST_GeneratePoints(ST_Buffer(

ST_GeomFromText(

  'LINESTRING(50 50,150 150,150 50)'

), 0.5, 'endcap=square join=round'), 1000);

     

 

If you want to generate random polygons, you could use ST_ConcaveHull or ST_AlphaShape around the section of a polygon you did a ST_GeneratePoints on

 

And then use something like https://postgis.net/docs/en/ST_Subdivide.html to chop up the polygons.

 

To get a linestring out of that (It will be closed), you can take the boundary of any of the above

 

https://postgis.net/docs/ST_Boundary.html

 

Hope that helps,

Regina

 

From: postgis-users <postgis-users-bounces at lists.osgeo.org> On Behalf Of Shaozhong SHI
Sent: Friday, September 8, 2023 7:56 AM
To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
Subject: [postgis-users] generate a geometry column of random point, line and polygon

 

Is a simple way to do this?

 

Regards,

 

David

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