Defining the Geographic Location for a DWG File.

Prem Gill

 Hi there, 

as a last resort after numerous attempts i've come seeking the wise help of the forums. 

I have DWG of a map. However, this has been converted from a PDF and therefore has no defined coordinates. It's currently defaults to the corner with a a Northing/Easting of 0,0. 

I'd like for it to be georeferenced and display the correct coordinates. How can I achieve this?

P.s. I have a DWG file of a different area, which DOES display the correct coordinates. Although its off a completely different area, so i'm not sure if it will help. 

Jason Bourhill

Hi Prem,

Check out the _ALIGN command. This allows you to move, rotate, scale one object relative to another. Have some detail here on using this command
http://www.cadconcepts.co.nz/aligning-images/

Regards,

Jason Bourhill

CAD Concepts

Richard Sands

You will need coordinates of at least one point and a knowledge of the scale of the PDF.
Generally I draw a line from a known point on the image, pdf, dxf, dwg to the coordinates of same known point in true coordinates.
Then I just move all from the assumed coordinates to the true coordinates.
IE from one end of the line to the other end.
Then just delete the line and any other extraneous detail.

That is a simple shift with no scale or rotate.

If you have coordinates of 2 points then again I draw lines between two points in both assumed and true coordinates and shift and rotate accordingly.

I don't deny the align command, just prefer this way as I have more control that I trust myself in.

I normally do the scale and rotate first then move in that order, but that's pure individual preference.

I use screen shots from Google or other aerial images that aren't georeferenced very often and it is very quick and precise (within constraints of the accuracy of known points).

If the distance separation is as here 5400000 metres then I would drag the assumed coordinate entity to within screen viewing distance of its true coordinates if that helps avoiding huge distances that leave all detail so small as to be invisible.

I also sometimes do this in a unique dwg then when I have done my shift scale etc I copy the entity from that dwg to its resting place using copy with base point as 0,0
and paste to 0,0.
I have had crashes mid stream with images that then leaves you wondering where things are at and avoids corrupting your working dwg.
Probably over cautious but lost data can be costly.

regards
Richard