[Freegis-list] dwg, dxf how to know reference system

[Umberto Nicoletti]

Autocad files do not have a notion of projection or reference system,
they simply model a 2-D cartesian system with 2 axys, x and y. The
reference is always the 0,0 point at the crossing of the two axis
which does not have an absolute coordinate representation. So for
instance, a DWG file about Europe and one about America will NOT share
a common absolute coordinate system but will simply reference this 0,0
point and the shapes will likely overlap.

To load the data in postgis you will have to extract the DWG/DXF data
into some intermediate form (ie shape files, or grass data) and then
georeference it which will probably mean some sort of translation and
transformation.
After that you can use postigs commands to load shapefiles or grass
layers into postigs.

Usually the tricky point is getting the data out of DWG/DXF into some
open format.

HTH,
Umberto

On 12/20/06, Antonello Moneta <a.moneta at portel.es> wrote:
> Hello, I am new in this mail list, so please be patient if I do
> something wrong, thanks.
>
> My problem is quite simple(I hope), but still I don't find any solution.
> I have to load in a postGis DB some maps form autocad environment(dwg,
> dxf), to use this dates with geoserver. I have a old version of autocad
> installed in my computer, but I cannot find how to know the reference
> system and projection. Some of you know how to do this, or know simple
> same program which is useful?
>
> Thank you a lot, Antonello Moneta
>
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