I have a Postgres table with some data created by using a shapefile. I need to find all records which intersect within 2 miles radius from a given latitude and longitude. I used some queries including the following one.
SELECT * FROM us_census_zcta WHERE ST_INTERSECTS(geom, CIRCLE(POINT(40.730610, -73.935242), 2));
But none of them worked. What I am doing wrong here? How can I get the results I need?
The SRID is 4269 (NAD 83).
EDIT: After Mike Organek pointed me out that I have switched the lat-long in the above query. And then I tried a few things and the following query gave me 1 record.
SELECT * FROM us_census_zcta WHERE ST_INTERSECTS(geom::geometry, ST_SETSRID(ST_POINT(-73.935242, 40.730610), 4269)::geometry);
But how can I use Circle and find records which intersect within 2 miles radius from that given lat-long?
What you're looking for is ST_DWithin
, which will check if records intersect within a given buffer. In order to use it with miles you better cast the geometry
column to geography
, as it then computes distances in metres:
For geography: units are in meters and distance measurement defaults to use_spheroid=true. For faster evaluation use use_spheroid=false to measure on the sphere.
SELECT * FROM us_census_zcta
WHERE
ST_DWithin(
geom::geography,
ST_SetSRID(ST_MakePoint(-73.935242, 40.730610), 4269)::geography,
3218.688); -- ~2 miles
Keep in mind that this cast might affect query performance if the indexes aren't set properly.
See also: Getting all Buildings in range of 5 miles from specified coordinates