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

[Santosh Gaikwad]

Hi,

 

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

 

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
location.)

 

 

Select *

   from california

   where setSRID(

            buffer(

              transform(GeomFromText('POINT(-121.962459
37.388364)',4326),2163),

              100

            ),

         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

http://www.saama.com

 

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