I would like to combine several catchment areas (points feature) into one catchment area. There are examples of my catchment areas.

enter image description here

Each area has one source (POI).I will use the combined area to create a map like this oneenter image description here(isochrone map by Anita Graser)

What should I do to get my areas combined?

  • If the values are the same ranges - you can merge the 2 point files and groupby source – Mapperz Jun 16 '17 at 16:03
  • Yes they're the same ranges. I've tried to merge them using merge vector layers (both SAGA and qgis geoalgorithms) but the result was the same with one of those layers – Afif Jun 17 '17 at 4:16
  • related: Create isochrone from multiple start points – underdark Jun 23 '17 at 14:51
up vote 1 down vote accepted

Here is a possible solution, starting with a query, that writes all distances in a single table first. The example uses OSM data imported with osm2pgrouting. Your attributes may have a different naming.

INSERT INTO data.distances SELECT 123456 AS source_id, a.*, b.id, b.the_geom FROM pgr_drivingDistance( 'SELECT gid AS id, source, target, cost_s AS cost, reverse_cost_s AS reverse_cost FROM osm.ways', 123456, 1000 ) AS a LEFT JOIN osm.ways_vertices_pgr AS b ON a.node = b.id; In the query above the source node ID is 123456, but you will run this query for each of your source nodes:

Then all your distances from each source node are stored in data.distances table and you can query the minimum distance to each node in your network:

SELECT DISTINCT ON (node) * FROM data.distances ORDER BY node, agg_cost ASC;

  • For your first source node start your query with CREATE TABLE data.distances AS, if the table doesn't exist yet. – dkastl Jun 18 '17 at 12:45
  • Thank you dkastl. What does osm.ways_vertices_pgr mean? Does it refer to vertices_pgr column on osm.ways table? – Afif Jun 21 '17 at 14:53
  • osm.ways_vertices_pgr is a table, that is also available after using osm2pgrouting. It contains a list of nodes, that are used as source and target ID's, and this table also contains geometry information of the nodes. You may have this in a different table or you can create it with pgr_createVerticesTable: docs.pgrouting.org/latest/en/… – dkastl Jun 22 '17 at 4:09
  • Hello dkastl, long time no see. I've tried your query and it works. Thank you! Does your query create line geometric table? – Afif Jul 5 '17 at 3:22
  • No, it doesn't. Btw., if your original question is answered, it may be good to mark it as resolved. – dkastl Jul 5 '17 at 15:36

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