[postgis-users] Adding geometry to an existing table

[Charlie Sharpsteen]

On Saturday, April 28, 2012 12:03:09 PM UTC-7, pcr... at pcreso.com wrote:
>
> Hi Shaun,
>
> You add a geometry column to the table, then run an update sql to populate 
> it.
>
> eg, assuming your table is called mytable, located in the public schema, & 
> you want to create a two dimensional point with lat/long coordinates 
> (EPSG:4326) called "geom":
>


And _assuming your lat/lon coordinates are referenced to WGS 84_ or, for 
small to medium scales, NAD 83---then EPSG:4326 is the right coordinate 
system. Not all lat/lon coordinates are equal.

For example the error between mis-identifying lat/lon in NAD 27 as lat/lon 
in WGS 84 is about half a city block.

-Charlie
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