[pgrouting-users] Create network with nodes at least every 50m

[Stephen Woodbridge]

Hi Adam,

ST_Segmentize returns a multilinestring and pgrouting does not know what 
to do with them so it takes only the first segment and ignores the rest.

  http://postgis.refractions.net/docs/ST_Segmentize.html

You will need to explode the into multiple linestrings. look at

  http://postgis.refractions.net/docs/ST_Dump.html

for how to do that.

What you probably should do is something like:

1. create a new edge table
2. process all you edges with segmentize and dump into the new table
3. then run pgr_createTopology on the new table
4. then try to route against the new table

-Steve

On 8/23/2014 8:16 PM, Adam Lawrence wrote:
> Hi,
>
> I have spent over a week trying to work this out. I have an existing
> road network and have used pgr_alphashape to try and get a 400m walking
> catchment from bus stops.
>
> But pgr_alphashape snapes to the nearest network node which means
> catchments returned are significantly smaller than 400m. I have
> therefore tried to create a new network with nodes every 50m using
> ST_Segmentize but I can't seem to get it to work.
>
> The function below is my attempt to loop through the existing network
> and run ST_Segmentize on each entry to return updated network with
> additional nodes but it only returns one record each time rather than a
> number of segmented entries.
>
> Any advice on how to make this work or alternative approach would be
> greately appreciated (especially given that following over a week and
> research it seems no one else has had this problem).
>
> Regards
> Adam
>
>
>
>
> DROP FUNCTION hutt_pax.my_test_function();
> CREATE OR REPLACE FUNCTION hutt_pax.my_test_function()
>    RETURNS TABLE (
> xid integer,
> xgeog geometry) AS
> $BODY$
> DECLARE
>      r hutt_pax.roads_wainuiomata%ROWTYPE;
> BEGIN
> FOR r IN
> SELECT *
> FROM hutt_pax.roads_wainuiomata
> LOOP
>
> xid := r.id <http://r.id>;
> xgeog := ST_Segmentize(
> r.geom,
> 0.050
> );
>
> RETURN NEXT;
> END LOOP;
>
> RETURN NEXT;    -- return final result
>
> END;
> $BODY$ LANGUAGE plpgsql STABLE;
>
> SELECT *
> FROM hutt_pax.my_test_function();
>
>
>
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