Hi ihab,
This function is from the pgRouting package, right? The function below
is actually not creating an id for every point in a line. Rather, it is
creating an id just for the endpoints of the line. In this manner,
pgRouting is trying to build a node network it can traverse in order to
perform dijkstra's shortest path algorithm. (I've always thought this
function should be named assign_node_id ... oh well).
Towards the end of the function, you'll see that the startpoints and
endpoints of the line are passed into the function point_to_id(geom,
tolerance) function. I think that it's in this function you should be
focusing your efforts, not this function.
The point_to_id function currently looks like this in the latest build.
CREATE OR REPLACE FUNCTION point_to_id(point geometry, tolerance double
precision)
RETURNS integer AS
$BODY$
DECLARE
row record;
point_id int;
BEGIN
LOOP
-- TODO: use && and index
SELECT INTO row id, the_geom FROM vertices_tmp WHERE
distance(the_geom, point) < tolerance;
point_id := row.id;
IF NOT FOUND THEN
INSERT INTO vertices_tmp (the_geom) VALUES (point);
ELSE
EXIT;
END IF;
END LOOP;
RETURN point_id;
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE STRICT
COST 100;
You'll want to change the filter on the SQL query from "WHERE
distance(the_geom, point) < tolerance" to something else (this one
currently doesn't use any index operator nor does it compute in 3D -
distance(geom, geom) does not currently use 3D values). I think it's
here you could compute the 3D distance between two points. If the
distance3D is less than some tolerance, they could be considered the same.
Hope that helps.
Cheers,
Kevin
eehab hamzeh wrote:
> Hello,
>
> I see your direction for index in 3d ... i have the function below which
> creating id for points of line. it assign the same id for points that
> have same x,y coordinates... i need it consider the z value ... i have
> no experience with plgsql can you please help me to develop it to
> consider the z values and assign the same id for points has same x,y,z
>
> Thanks
> ihab
>
>
>
>
eehab hamzeh wrote:
Hello,
I have the following function which check if two (or more) points are
one, the function just consider the x,y coordinates. can any body help
me to modify it to check z-index also.
Thanks
Ihab
below is the function
-- Function: assign_vertex_id(character varying, double precision,
character varying, character varying)
-- DROP FUNCTION assign_vertex_id(character varying, double precision,
character varying, character varying);
CREATE OR REPLACE FUNCTION assign_vertex_id(geom_table character
varying, tolerance double precision, geo_cname character varying,
gid_cname character varying)
RETURNS character varying AS
$BODY$ DECLARE
points record; i record; source_id int; target_id int; pre varchar; post
varchar;
BEGIN
BEGIN
DROP TABLE vertices_tmp;
EXCEPTION
WHEN UNDEFINED_TABLE THEN
END;
CREATE TABLE vertices_tmp ( id serial );
EXECUTE $q$ SELECT addGeometryColumn('vertices_tmp', 'the_geom',
(SELECT srid FROM geometry_columns WHERE f_table_name='$q$
quote_ident(geom_table) $q$') , 'POINT', 4) $q$;
CREATE INDEX vertices_tmp_idx ON vertices_tmp USING GIST (the_geom);
pre = ;
post = ;
FOR i in EXECUTE 'SELECT count(*) as t from ' quote_ident(geom_table) '
WHERE _NumGeometries?_
<http://pgrouting.postlbs.org/wiki/NumGeometries>?('
quote_ident(geo_cname) ') is not null' loop
IF (i.t > 0) THEN
pre = 'geometryN('; post = ' , 1)';
END IF;
END LOOP;
FOR points IN EXECUTE 'SELECT ' quote_ident(gid_cname) ' AS id,'
' startPoint(' pre quote_ident(geo_cname) post ') AS source,' '
endPoint(' pre quote_ident(geo_cname) post ') as target' ' FROM '
quote_ident(geom_table) loop
source_id := point_to_id(points.source, tolerance); target_id :=
point_to_id( points.target, tolerance);
EXECUTE 'update ' quote_ident(geom_table)
' SET source_id = ' source_id
', target_id = ' target_id
' WHERE ' quote_ident(gid_cname) ' = ' points.id;
END LOOP;
RETURN 'OK';
END; $BODY$
LANGUAGE 'plpgsql' VOLATILE STRICT COST 100;
ALTER FUNCTION assign_vertex_id(character varying, double precision,
character varying, character varying) OWNER TO postgres;
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