pgRouting

Forum #18 - Topic #70 - Message List

Shooting Star Query

Hi,

First of all sorry for asking another question again :( But I am really interested in this project and trying alot of functions :)

I am trying to play a bit with the Shooting Star Query, since I need it for one-ways.

I am trying this query : SELECT gid, the_geom

FROM shootingstar_sp('streets',

give_source('POINT(640905 225230)',1000,200), give_target('POINT(640982 225439)',1000,200), 2000,'length',true,true);

and also tried this query : select rt.gid, rt.the_geom, length(rt.the_geom), streets.gid from streets, (select gid, the_geom from shootingstar_sp( 'streets', give_source('POINT(640905 225230)',1000,200), give_target('POINT(640982 225439)',1000,200), 5000, 'length', true, true) )as rt

For half of the results both edge_ids are the same, however when I project the result on a shapefile then on QGis on my map, the points where the route should start and end are FAR from the points I selected.

The functions give_source and give_target are functions I gave to transfrom the Point to the source colum and this is the function : -- Function: give_source(text, integer, integer)

-- DROP FUNCTION give_source(text, integer, integer);

CREATE OR REPLACE FUNCTION give_source(text, integer, integer)

RETURNS integer AS

$BODY$

DECLARE

pojnt ALIAS FOR $1; box ALIAS FOR $2; dist ALIAS FOR $3;

r_source INTEGER;

BEGIN

SELECT source INTO r_source FROM streets s WHERE

( the_geom && expand (pointfromtext(pojnt),box) and distance (s.the_geom , pointfromtext(pojnt)) < dist )

ORDER BY distance (s.the_geom , pointfromtext(pojnt)) ASC LIMIT 1;

RETURN r_source;

END; $BODY$

LANGUAGE 'plpgsql' VOLATILE;

ALTER FUNCTION give_source(text, integer, integer) OWNER TO yancho;

I know it should be something stupid that I am doing, but really am out of ideas why it is not working. For sure the routing is being done well, but the start / end points are wrong, so it should be something from the give_source / give_target problem. BTW I used these two functions for my astar_sp_delta testing and it worked perfectly :

SELECT gid, AsText?(the_geom) AS wkt

FROM astar_sp_delta(

'streets', (select give_source('POINT(640905 225230)',1000,200), (select give_target('POINT(640982 225439)',1000,200), 3000 );

";

Any ideas will be extremely appreciated and keep up the good work :)

yancho
11/26/07 19:12:35
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  • Message #265

    I am including this info maybe it helps you better tackle this problem :

    As you can see on the paste here : http://yancho.pastebin.com/f7f44a0c2

    The first result row of astar_sp_delta is : 40617;"MULTILINESTRING((640920.707155369 225441.381903503,640919.710413482 225419.024734874,640904.400352 225231.230885577))"

    .. Which is very near the POINT : POINT(640905 225230),

    However the first result row of shootingstar_sp is : 791;"MULTILINESTRING((629357.137492173 222486.61416491,629357.137492172 222526.524103276))" followed by these two :

    47462;"MULTILINESTRING((629357.137492172 222526.524103276,629355.842055444 222559.004436553))" 44423;"MULTILINESTRING((629355.842055444 222559.004436553,629354.394306192 222605.962730528))"

    Which shows clearly how far it is from the starting point : POINT(640905 225230)

    Also I tried this function :

    SELECT * FROM shortest_path_shooting_star('

    SELECT gid as id,

    source::integer, target::integer, length::double precision as cost, rcost::double precision as reverse_cost, x1, y1, x2, y2, rule, to_cost

    FROM streets',

    give_source('POINT(640905 225230)',1000,200), give_target('POINT(640982 225439)',1000,200),

    false,true);

    Highted and pasted here : http://yancho.pastebin.com/f7a2f7e2b

    Which is giving me these 3 rows as my first resultset : 13065;791;39.9099383660941 13066;47462;32.5061564333317 21733;44423;46.9806061157797

    Which have the same gid as the first 3 resultset given from shootingstar_sp .. so it is quite obvious I am giving the functions the wrong starting location / ending .. any one can shed some light on what I should fix please?

    Thanks and regards

    Matthew

    yancho
    11/27/07 02:02:52
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