Hi Peter,
Here is a link to OSGeo workshop that should be a helpful premier on the
issue in general and provides a solution to your problem through the use
of PostGIS's geography type:
http://workshops.opengeo.org/postgis-intro/geography.html
If you are dealing with a fairly well define area, say the West Coast of
the US and Canada, then you might consider reprojecting your data out of
NAD83 (North American Datum of 1983) geographic (lon/lat) coordinates
(EPSG: 4269) into Euclidean coordinates (such as NAD83 UTM 10N), and
then you can use the standard st_area tool and the result will be in meters.
Dan
On 05/20/2011 11:57 AM, Peter Hsu wrote:
I have a simple question. I've loaded up shape files from the tigerline US
census bureau. Everything works fine, but I'm trying to find the area of a
geometry in meters. However, I'm only able to get the area in SRID units.
How can I convert from SRID units to meters? Is this a linear conversion? Or
is it dependent on the latitude of the area in question?
The SRID for the tigerline files is 4269
Peter
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