[postgis-users] Fw: MakeLine into new layer

[Brent Wood]

Off the top of my head...
That returns the longest straight line within a polygon. 

I suggest your workflow is to create a target table first (with a column for the id of the polygon it came from), so you have somewhere to put the linestrings (not necessary, but I find it tidier).
eg:
create table long_lines (id integer primary key), geom  geometry(LINESTRING, <SRID>);
then run your query...
INSERT INTO long_linesSELECT id,  
   ST_MakeLine(St_LongestLine(
    (SELECT geom FROM floodplainw
    WHERE id = 1),
    (SELECT geom FROM floodplainw
    WHERE id = 1))
); 

Cheers
Brent Wood

      From: Shane Carey <careyshan at gmail.com>
 To: postgis-users at lists.osgeo.org 
 Sent: Tuesday, October 23, 2018 8:07 AM
 Subject: [postgis-users] MakeLine into new layer
  
Hi,I am trying to find the longest line of a polygon and insert it into a new line. I can create the makeline as in the code below but cannot create a new layer out of it using the INTO keyword. Any help would be appreciated. Thanks
SELECT 
   ST_MakeLine(St_LongestLine(
    (SELECT geom FROM floodplainw
    WHERE id = 1),
    (SELECT geom FROM floodplainw
    WHERE id = 1))
);

Le gach dea ghui,
Shane CareyGIS and Data Solutions Consultant
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