[postgis-users] How do you obtaining a WGS-84 (4326) coordinate from a coordinate that has no SRID

[Eric B. Powell]

ILAN BENISTY wrote:
> Hi,
>
> I am dealing with a problem where I am importing an AutoCAD 
> description of an airport (DXF) into PostGIS.
> I have a Python script which will import each coordinate to a PostGIS 
> geometry with SRID = -1 (since I do not have real world coordinates, 
> but Cartesian coordinates from a point of origin).
> I do, however, have a lat/long reference point, which represents the 
> origin of my x/y CAD coordinates.
> I would like to be able to store my CAD coordinates points as Long/Lat 
> (SRID=4326).
> Any suggestions?
>
> Thanks,
>
> Ilan
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What country is the site in? What units are used for the drawings grid? 
Do you know the geographic datum?

It may require a fair amount of pre-processign before the data can be 
accurately (de)projected to LatLong.

Once the details of the drawing grid are known, there is a python 
wrapper for Proj4 which could be used to (de)project the points on the 
way into the database.

Eric