[postgis-users] How does PostGIS know Units?

[Paul Ramsey]

Yes, PostGIS assumes all your units are the same. Which means that if 
you are working in degrees, buffer will also work in degrees. Which is 
probably not what you want. You will want to choose a planar projection 
to work in that is suitable to your data.

Mark Fenbers wrote:

> OK, I'm getting better, but still very green using PostGIS.
> 
> Given the SQL excerpt construct:
>     buffer(PointFromText('POINT(39.0 -83.4)'),125.0)
> How do I tell PostGIS that the (39.0 -83.4) represents latitude and 
> longtitude (instead of some arbitrary x,y), and that 125.0 represents 
> kilometers (instead of meters, or miles)?  As given, PostGIS thinks all 
> values in the construct have the same units.
> 
> Mark
> 
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