Re: [postgis-users] distance_spheroid and index files
wanxiangqian at 163.com
wanxiangqian at 163.com
Fri Feb 25 23:26:02 PST 2005
Hi,
1 Extract the x,y (longitude,latitude) from the point geometry into two fields of places.
2 Use normal index to implement fast query.
The latitude optimization may be easy.
geom = point_of('berlin');
x0 = X(geom);
y0 = Y(geom);
rl = range_of_longitude(x0,10km);
rt = range_of_latitude(10km);
select * from places where x > x0 - rt and x < x0 + rt and y > y0 - rl and y < y0 + rl and distance_spheroid(
location_geom,
(select location_geom from places where place = 'Berlin'),
'SPHEROID["WGS 84",6378137,298.257223563]'
)/1000 < 10;
Wish you good luck!
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