How to convert points data to polygon, enter image description here so as to form polygon from exterior point as shown above


I would create a geometry collection from the points using st_collect(): http://postgis.net/docs/ST_Collect.html

Then I would create convex hull from the point collection: http://postgis.net/docs/ST_ConcaveHull.html

If you have a table of point geometries called testpoints where geometry column name was the_geom, this should create the polygon that you are looking for:

SELECT st_astext(st_concavehull(st_collect(the_geom),0.99))
  FROM myschema.testpoints;
  • If you are looking for a good PostGIS book, the new PostGIS Cookbook from PACKT is very good. – DavidF Mar 21 '14 at 18:33
  • thanks david, your query works on a simple points, but not good enough on complex points. – user28344 Mar 22 '14 at 1:59
  • Can you provide an example or define what you mean by complex points? Multi-point features? I am pretty sure that the query that I provided will correctly solve the problem that you diagrammed. – DavidF Mar 22 '14 at 18:01
  • This my point <img src="duniabimbel.com/blog/img/files/Untitled.png"> i use concavehull with 0.5 % – user28344 Mar 24 '14 at 7:53
  • I think the trick is that there is no magic solution that fits all point sets. The computer doesn't know what you want it to look like in the end. st_concave_hull starts with a convex hull and then 'shrink wraps' it based on your value for target percent. I would increase the value of your target percent. – DavidF Mar 24 '14 at 13:27

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