Hi Alexandre,
perhaps you could run ST_Simplify in a function with a while loop
testing over ST_NPoints:
CREATE OR REPLACE FUNCTION simplify_npoints(geometry, integer)
RETURNS geometry AS
$BODY$
DECLARE
InGeom alias for $1;
maxpoints alias for $2;
npoints integer;
tolerance float;
outGeom geometry;
Begin
npoints:=ST_NPoints(InGeom);
outGeom:=InGeom;
tolerance:=0.0;
while npoints > maxpoints loop
tolerance:=tolerance + 0.001;
outGeom:=ST_Simplify(InGeom, tolerance);
npoints:=ST_NPoints(outGeom);
end loop;
return outGeom;
End;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION simplify_npoints(geometry, integer) OWNER TO postgres;
I don't know if it will work (didn't test). And perhaps bigger iteration
steps would be sufficient, too...
Good luck! Regards,
Birgit.
Am 24.10.2012 14:29, schrieb Alexandre Saunier:
Hello.
I would like to know if some tools are available in PostGIS to
simplify a linestring to a given maximum number of points.
A bit like the "simplify,count=<...>" filter in GPSBabel:
http://www.gpsbabel.org/htmldoc-development/filter_simplify.html
ST_Simplify is close to what I need but I don't know in advance what
tolerance to use, only the final maximal number of points.
Is there a way to do that kind of simplification with PostGIS?
Thanks!
Alexandre
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