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The ST_DWithin document says , the third parameter(distance) is in meters. But when I execute some query , it seems it takes the 3rd parameter as 'degree' ? Here is my simplified table structure : > \d+ theuser; Table "public.theuser" Column | Type | Modifiers | Storage | Description ----------+------------------------+-----------+----------+------------- id | bigint | not null | plain | point | geometry | | main | Indexes: "theuser_pkey" PRIMARY KEY, btree (id) "point_index" gist (point) Referenced by: ... Has OIDs: no All points are stored with SRID=4326. And this is the query : > select * from theuser where ST_DWithin(point , ST_GeomFromText('POINT(120.9982 24.788)',4326) , 100 ); It takes the 3rd parameter (100) as 'degree' , so it returns all data , I have to narrow down to 0.001 to find nearby points. But how do I directly pass meters as 3rd parameter (I don't want to do meter/degree transformation ) ? What's wrong with my query ? why postgreSQL doesn't take it as meters as document says ? Environments : > select version(); version ----------------------------------------------------------------------------------------------------------- PostgreSQL 8.4.9 on i486-pc-linux-gnu, compiled by GCC gcc-4.4.real (Ubuntu 4.4.3-4ubuntu5) 4.4.3, 32-bit > SELECT postgis_lib_version(); postgis_lib_version --------------------- 1.4.0 If it is the SRID that causes this problem , what SRID directly makes use of 'meter' as the unit ? (I tried transforming to SRID=2163 , but still in degree) Thanks.

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