[postgis-users] srid

[Andy Anderson]

On May 26, 2008, at 3:06 PM, Bob Pawley wrote:

> However, I attempting to interpret functions made for geographic  
> data to use with geometric data.
>
> I have PostgreSQL tables which represent engineering processes.
>
> I want to display that data in a graphical form - hopefully using  
> Postgis - - - if I can translate the functions (or the Postgis  
> concept) into a form that I can use.

Hmmm... if all you want to do is display X-Y data, I would suggest  
using geographic coordinates, e.g. SRID = 4326 (WGS84 datum), which  
most programs will display by default with X and Y rectilinear.

However, you earlier said you wanted to use ST_Transform(geometry,  
integer), which implies you want to switch between different  
geographies.

So it sounds like you need to pick a particular projection for your  
work.

Is your geography spherical or spheroidal? If so, you might want to  
define your own datum. If not, you'll need to use a projection to a  
flat surface. What's more important, that it be conformal  
(equiangular) or equal area or that it preserve distance in one  
direction?

-- Andy