Creating Polygons from Points in Carto

Question

Using Carto, I am trying to create shapefiles of regions using points(Link to Dataset in Carto ) with a shared column value to group by.   I've included 3 photographs. 1st photograph of the points outlining the shape. the second photo is my desired result which I have drawn out by hand. The third photo is an attempt that doesnt meet my desired result..

I am using the analysis tool provided by Carto, running a concave hull and have tried various target percent values and without the desired results. For this example I've included a target percent of 80 and the result is shown in a photograph at the bottom. The code is provided below

SELECT row_number() over() as cartodb_id,
         territoryid as category,
         ST_ConcaveHull(
             ST_Collect(the_geom), 
             0.8, 
             false
          ) AS the_geom,
         count(1) as count_vals
    FROM (
         SELECT *
           FROM ( SELECT * FROM "st-braund".bd_regions_1 ) _camshaft_category_filter
          WHERE territoryid IN (3)
         ) _analysis_source
GROUP BY territoryid

Sbraund · Answer

The solution I found for the above problem was to

Create Lines from the points --> Close the Lines --> then make a polygon from closed lines.

SELECT row_number() over() AS cartodb_id, *,
  ST_Length(the_geom_webmercator::geography) as length FROM (
  SELECT territoryid as category
   , ST_MakeLine(the_geom ORDER BY bd_territories_coords_id asc) AS the_geom_webmercator 
  FROM (
    SELECT * FROM "st-braund".template_localities_1 ) _line_sequential
  GROUP BY territoryid ) _cdb_analysis_line_sequential

Creating Polygons from Points in Carto

One Answer

Add your own answers!

Ask a Question