Re: [postgis-users] get the biggest intersection

[Denis Rouzaud]

Hi Stefen, Hi Fred,

Thank you both for your answer.
There was effectively an invalidity in a geometry.
Now my function is working great.

But still, do you think it is a good idea to use an "order by" and 
"limit 1" to have the desired result?

Thanks again,

Denis

On 06/20/2012 04:27 PM, Stephen Woodbridge wrote:
Try:

select count(*) from polygons where not isvalid(geometry);

if count > 0 then

select count(*) from polygons where not isvalid(geometry) and not 
isvalid(st_buffer(geometry, 0.0));

you can do an update to fix these:

update polygons set geometry=st_buffer(geometry, 0.0) where not 
isvalid(geometry);


-Steve W

On 6/20/2012 7:54 AM, Denis Rouzaud wrote:
Hi all,

I have a table of line and a table of polygons. For a given line, I
would like to get the polygon which has the biggest intersection with
the line.
I tried something like this:

CREATE OR REPLACE FUNCTION distribution.get_zone_id(geometry) RETURNS
integer AS '
     DECLARE
         inputgeom ALIAS FOR $1;
         id_poly integer;
     BEGIN
         SELECT id INTO id_poly
             FROM  polygons
             WHERE ST_Intersects(inputgeom,geometry) IS TRUE
             ORDER BY ST_Length(ST_Intersection(inputgeom,geometry)) 
DESC
             LIMIT 1;
         RETURN id_poly;
     END
' LANGUAGE 'plpgsql';

But I have the following error:
ERROR:  Error performing intersection: TopologyException: side location
conflict at 553524.92178241001 147945.03792368001

If anyone has any idea, tip or whatever, it is very welcome!

Greetings,

Denis
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