How to select all points near a line? - postgis

Question

I have a linestring:
LINESTRING( -43.0965167 -22.8808585,-43.0980368 -22.8807975,-43.0986518
-22.8807735,-43.0990955 -22.8807701,-43.0991492 -22.8807697,-43.1005956
-22.8807353,-43.1013221 -22.8807107,-43.1016904 -22.8807003,-43.1019484
-22.8806902,-43.1020398 -22.8806866,-43.102591 -22.8806801,-43.1029336
-22.8806666,-43.1036051 -22.8806402,-43.1039349 -22.8806272,-43.1042967
-22.880613,-43.1061912 -22.8805398 )
Now I can select all points at a distance "x" from this line ( around the line ). I already tried Find the nearest points along the linestring in specified distance limit and order with no success ( always take a lot of points in a box like distribution ). This is a piece of code I started to write:
select p.way,p.name from planet_osm_point p where ST_DWithin(
ST_Transform( theLineGeom, 4326), ST_Transform( p.way,4326 ), 0.9)
limit 50;

Answer 1

I think you are getting lots of points because ST_DWithin uses the unit of the geometries srid to perform the calculation.
boolean ST_DWithin(geometry g1, geometry g2, double precision distance_of_srid);
So you are getting all the points with 0.9 degrees from your linestring.
You could use
boolean ST_DWithin(geography gg1, geography gg2, double precision distance_meters);
converting your geometries to geography.
Otherwise you could use another srid.

Answer 2

Solved. I just get too many points because the limit was too big. If I have 2 points near the route and tell the query to give me the first 50 then 48 points will be far from the line but inside the bounding box. This is why the box like distribution I saw.
select * from pointscanner('<geomRoute_WILL_BE_HERE>') where round(distance::numeric, 5) < 500 /* meters */
CREATE OR REPLACE FUNCTION public.pointscanner( IN routeGeometry text)
RETURNS TABLE(way geometry, name text, distance double precision, tags hstore, operator text, admin_level text, z_order integer) AS
$BODY$
DECLARE
geomRoute geometry;
routeBB box2d;
BEGIN
geomRoute = ST_GeomFromText('MULTILINESTRING(
(-43.1761935 -22.90642,-43.1755606 -22.9064116,-43.1754828 -22.9064106,-43.1753675 -22.9064091),
(-43.176696 -22.9064062,-43.1761935 -22.90642),(-43.176805 -22.9064027,-43.176696 -22.9064062),
(-43.1776911 -22.9049927,-43.1776625 -22.9050849,-43.1775227 -22.9055527,-43.1775045 -22.9056041,-43.1774504 -22.9057582),
(-43.1782012 -22.9036858,-43.1778613 -22.9045254,-43.1777841 -22.9047287,-43.1777446 -22.9048326,-43.1777179 -22.9049164,-43.1776911 -22.9049927),
(-43.1772218 -22.9063929,-43.1771252 -22.9063944,-43.1771118 -22.9063946,-43.1769202 -22.9064008,-43.176805 -22.9064027),
(-43.1774504 -22.9057582,-43.1773182 -22.9061373,-43.1772868 -22.9062205,-43.1772218 -22.9063929),
(-43.1834587 -22.9028997,-43.1833984 -22.9028862,-43.1830022 -22.9027778,-43.1825446 -22.9026278,-43.1821151 -22.9024891,-43.1816491 -22.9023374,-43.1815912 -22.9023186,-43.1813461 -22.9022388),
(-43.1793173 -22.901581,-43.1791549 -22.9015418,-43.179105 -22.9015365,-43.1790457 -22.9015482,-43.1790174 -22.9015689,-43.178994 -22.9016082),
(-43.1788184 -22.9020931,-43.1786726 -22.9025241,-43.1786518 -22.9025769,-43.1786063 -22.9026931),
(-43.1813461 -22.9022388,-43.1806028 -22.9019969,-43.1805417 -22.901977,-43.1799074 -22.9017705),
(-43.1799074 -22.9017705,-43.1797658 -22.9017244,-43.1793732 -22.9015989,-43.1793173 -22.901581),
(-43.178994 -22.9016082,-43.1788184 -22.9020931),(-43.1784337 -22.9031366,-43.1782012 -22.9036858),
(-43.1786063 -22.9026931,-43.17848 -22.9030174,-43.178461 -22.9030662,-43.1784337 -22.9031366))',4326);
routeBB := ST_Extent(geomRoute);
RETURN QUERY
SELECT pt.way, pt.name, ST_Distance( geomRoute, ST_Transform(pt.way,4326) ) * 111195 as distance,
pt.tags, pt.operator, pt.admin_level, pt.z_order
FROM planet_osm_point pt
where routeBB && ST_Transform(pt.way,4326);
END; $BODY$
LANGUAGE plpgsql VOLATILE