[postgis-users] Lat/Long,geometry and buffer

Santosh Gaikwad Santosh.Gaikwad at saama.com
Wed Jul 4 04:20:18 PDT 2007



I have US address which have been geocoded to get latitude and


I am following the below steps


1. Add column


SELECT AddGeometryColumn( 'public', 'california', 'the_geom', 4326,
'POINT', 2 );


2. Populate geometry


UPDATE california

        SET the_geom = PointFromText('POINT(' || longitude || ' ' ||
latitude || ')',4326)


3. Spatial query (I would like to build the spatial query for listing
out the locations for a given radius of 100 meters from a particular



Select *

   from california

   where setSRID(





         2163)&& transform(the_geom, 2163)


This returns back me the locations with specified 100 meters radius.
This seems to be working fine but I am not confidant about it. When I
checked out SRID 2163 in spatial_ref_sys table, it says that the
projection is US national atlas equal area and unit is meters. I would
like to know whether this projection covers whole USA satisfactorily or
not. When I am using openjump by bringing postgis data into it, I can
not see the distance in meters on map. Why it is so? Thus this means
SRID 2163 has been used only to transform the projection. 


Next I want to work on whole USA data. Please kindly let me know whether
I am following the correct steps or not?



Santosh Gaikwad

Senior Software Developer

Saama Technologies (India) Pvt Ltd.
6th Floor West Wing, Marisoft III, 
Marigold Premises, Kalayani Nagar,
Pune - 411014. India
Phone : +91 20 66071319 Extn: 397

Mobile: +91-9422005927
E-mail :Santosh.Gaikwad at saama.com



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