[postgis-users] Polygon area in meters

[Kemal Bayram]

Thanks Ibo but I forgot to mention I need one transform that works with all
locations, but that it does not need to be accurate so +/- 10% would be
acceptable.  I need to catagorise some areas by size so for example 100-1000
m2, 1000-10000 m2 for visual purposes.
 
  _____  

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of ibrahim
saricicek
Sent: 09 February 2010 15:47
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Polygon area in meters


Hi;

one method...
ST_Distance_Spheroid(point_x, point_y, 'SPHEROID["WGS
84",6378137,298.257223563]');

the other method create a new geometry (the_geom_epsg) column ansd find the
exaxt EPSG code for your region (i prefer 2321 for middle Turkiye ED50 /TM
33)

update table set the_geom_epsg=st_transform(the_geom, epsg)
then use st_area..

Regards..
IBO..


On Tue, Feb 9, 2010 at 3:40 PM, Kemal Bayram <kemal at cins.co.uk> wrote:


Hi,
 
I'm current working with data in long/lat (wgs84) format and using
st_distance_spheroid to calculate the length of my linestrings in meters.  I
now need to calculate the area of my polygons and am wondering what the
easiest way of doing this would be? 
 
I am thinking projecting the polygon with an equal area projection and then
using st_area on the result.  Anyone have any ideas on suitable
projections/SRIDS?
 
Regards
 

Kemal

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