dijkstra (#16) - Solution for getting "parts" of lines (#281) - Message List

Dear users,

the pgrouting algorith as knows has the problem that after clicking in a map in the most cases not the "whole" route is visualised (or a bit too much), see it here:

 http://www.kneipenculture.de/routing_works.png

With the following function a point on a multiline is caught:

---

geometry)

RETURNS geometry AS

$BODY$ DECLARE

mindistance float8; nearestlinestring geometry; nearestpoint geometry; i integer;

BEGIN

mindistance := (distance(apoint,amultils)+100); FOR i IN 1 .. NumGeometries?(amultils) LOOP

if distance(apoint,GeometryN(amultils,i)) < mindistance THEN

mindistance:=distance(apoint,GeometryN(amultils,i)); nearestlinestring:=GeometryN(amultils,i);

END IF;

END LOOP;

nearestpoint:=line_interpolate_point(nearestlinestring,line_locate_point(nearestlinestring,apoint));

RETURN nearestpoint;

END; $BODY$

LANGUAGE 'plpgsql' IMMUTABLE STRICT;

---

....and with the following function the part between the point and the (before that) missing routing-part is drwan:

---

CREATE OR REPLACE FUNCTION schnittpunkt(gid_a integer,gid_b integer,start geometry)

RETURNS geometry AS

$BODY$ DECLARE intercept_point geometry; number_of_points integer; first_point_of_geometry geometry; j integer; point_geom geometry; line text; mywkt text; p text; new_factor integer; endgeometry geometry[] := '{}';

BEGIN

RAISE NOTICE 'Here we go........';

--Give me the intercept point of two geometries we use...... intercept_point:= ST_astext(intersection(a.the_geom, b.the_geom)) from (select the_geom from ways where gid=$1)a, (select the_geom from ways where gid = $2) b;

RAISE NOTICE 'intercept_point %',astext(intercept_point);

-- Give me the number of points of the geometry we touch with the start-point number_of_points:=ST_NumPoints(the_geom) from ways where gid=$1;

mywkt:=; line:=;

RAISE NOTICE 'Numer of points in that geometry is %',number_of_points;

first_point_of_geometry:=PointN(c.the_geom,1) from (select (the_geom) from ways where gid=$1)c,ways where gid=$1;

-- If intercept_point and first point of geometry (with start point) is equal IF astext(intercept_point)=astext(first_point_of_geometry) THEN

RAISE NOTICE 'Equal!!';

FOR j IN 1 .. number_of_points LOOP

point_geom:=PointN(c.the_geom,j) from (select (the_geom) from ways where gid=$1)c,ways where gid=$1;

RAISE NOTICE 'Call: %',j; endgeometry[j]:=point_geom;

RAISE NOTICE 'The point is %',astext(point_geom);

line:=;

line:= line X(endgeometry[j])' 'Y(endgeometry[j])', 'X(endgeometry[j-1])' 'Y(endgeometry[j-1]);

-- A line is build

line:='LINESTRING''(' line ')';

SELECT INTO p ST_intersects(line,buffer($3,1));

IF j=1 THEN

mywkt:= mywkt X(endgeometry[j])' 'Y(endgeometry[j])', '; END IF;

IF p!= 't' THEN RAISE NOTICE 'The start point does not touch a part of a multiline';

mywkt:= mywkt X(endgeometry[j])' 'Y(endgeometry[j])', ';

END IF;

IF p = 't' THEN RAISE NOTICE 'Interesting: Start point touches part of multiline, we replace it!!';

mywkt:= mywkt X($3)' 'Y($3);

mywkt:='MULTILINESTRING''((' mywkt '))'; RAISE NOTICE 'We have got the new geometry: %',mywkt; RETURN mywkt; END IF;

END LOOP;

ELSE

-- Ok, intercept_point and first point of geometry (with start point)are not equal -- We have to go "thr other way round"

FOR j IN 1 .. number_of_points LOOP

new_factor:=number_of_points+1-j;

point_geom:=PointN(c.the_geom,new_factor) from (select (the_geom) from ways where gid=$1)c,ways where gid=$1;

RAISE NOTICE 'Call number: %',j; endgeometry[j]:=point_geom;

RAISE NOTICE 'The point is at %',astext(point_geom);

line:=;

line:= line X(endgeometry[j])' 'Y(endgeometry[j])', 'X(endgeometry[j-1])' 'Y(endgeometry[j-1]);

line:='LINESTRING''(' line ')';

SELECT INTO p ST_intersects(line,buffer($3,1));

IF j=1 THEN

mywkt:= mywkt X(endgeometry[j])' 'Y(endgeometry[j])', '; END IF;

IF p!= 't' THEN RAISE NOTICE 'The start point does not touch a part of a multiline';

mywkt:= mywkt X(endgeometry[j])' 'Y(endgeometry[j])', ';

END IF;

IF p = 't' THEN RAISE NOTICE 'The start point touches a part of a multiline';

mywkt:= mywkt X($3)' 'Y($3);

mywkt:='MULTILINESTRING''((' mywkt '))'; RAISE NOTICE 'The geometry is %',mywkt; RETURN mywkt; END IF;

END LOOP;

END IF;

RETURN mywkt;

END; $BODY$

LANGUAGE 'plpgsql' IMMUTABLE STRICT;

---

I will integrate it in here http://pgrouting.postlbs.org/wiki/WorkshopOL2.7andOSM

within the next days to make this clearer.

Best regards, Kai