PostGIS : nearest linestring to a given point

Question

Hi guys. I've been using PostGIS in a long time now but never had to use the LINESTRING geometry ... yet! :)

Here's what I would like to do : I have a table of linestrings (representing streets of a given city, SRID 3395) and I would like to find the nearest linestrings to a given point (GPS position, SRID 4326).

The solution I found is to select all the linestrings within my point using the expand() method and determine the distance between each linestring and my point using the ST_Distance() method.

Here's the SQL :

SELECT myLineId, myLineName, ST_Distance(ST_Transform(GeomFromText('POINT(LON LAT)',4326),3395),myLineGeom) AS myLineDistance
FROM myLines
WHERE myLineGeom && expand(ST_Transform(GeomFromText('POINT(LON LAT)',4326),3395), 100)
ORDER BY myLineDistance;

The results I get looks pretty OK but I have the feeling something is wrong in my implementation.

1) Do you guys thinks the expand() can get all the concerned linestrings?

2) Do you guys thinks the ST_Distance() is the right method to use? I guess I'm doing it wrong since the distance I would like to get is the smallest distance between the point and my line and not the distance between the point and one point of the linestring.

Thanks for any tips!

Answer 1

http://gis.stackexchange.com/questions/2061/postgis-nearest-linestring-to-a-given-point