Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I have got an Audocad .dwg file which is based on some location of sweden. But i dont know what is the internal projection of this file? how i get projection information from this .dwg file. Actually When i convert this .dwg file into .shp file by using FME software, then it requires projection information (source file projection) for converting it into shapefile (the target format), and i dont know what is the projection of this .dwg file? Is there any way to get to know about the projection of source file .dwg ?

share|improve this question
    
likely to be one of these two - mapref.org/MapProjectionsSE.html –  Mapperz May 4 '11 at 18:42
add comment

2 Answers 2

up vote 5 down vote accepted

There may or may not be projection information in the autocad drawing. If there is it can be read only with one of the GIS products from Autodesk (i.e. map3d, civil3d, mapguide).

You will need to either...
1. use an autodesk product to discover the assigned crs.
2. contact the originator and find out the crs.
3. convert to a format you can use (probably with no transformation), and then begin to discover the crs.
4. project the data with esri arcmap (which will create a world file for the dwg). [I don't normally use this method]
5. As Dano suggest rubbersheet (use a copy)

If you can send along the dwg or make it available for open online (autocad can open online dwg), I can take a look for you.

If there is an item in your dwg that is identifiable on the ground or another map, you can open the dwg with a free viewer (autodesk trueview), identify the coordinates at the known point and then begin to ascertain the correct prj.

share|improve this answer
    
@ Brad - can't he just "force" it in to his projection of choice? I just can't remember how it was done because I didn't use CAD at the time .... but I think my old boss used a technique called rubber sheeting. I honestly don't know how he discovered data that were a match to perform the stretch .... but I'm certain he did this in under an hour. Any thoughts? –  Dano May 5 '11 at 2:43
    
Rubbersheeting does apply to vector also. Using the force method would work as long as the grid were close to the same. As for instance when you force a lat lon to a state plane or (sweden local) projection the known points around the edge of the data are what you use to "force" it. Everything in the middle goes along for the ride. lat lon to sp is pretty ugly. Perhaps if we could see a screen shot? –  Brad Nesom May 5 '11 at 4:50
    
rubbersheeting is available in any of the GIS products and ESRI, QGIS, GRASS, Plus all the others and not neccessary unless it is in "no projection". If the original data was in a projection and the coordinates of the drawing are related to that projection it would be easiest and most accurate to define the projection. –  Brad Nesom May 5 '11 at 4:55
add comment

Continuing with my comment to Brad .... I'm going to have a crack at answering this one. I did a quick Google search for rubber sheeting in CAD. I found this:

Rubber Sheeting a Drawing with no Coordinate System

I just skimmed through, but I think this will solve your problem.

share|improve this answer
    
Ok ... I just read a bit further. I think this method is only used with raster data. Check this link out too. Hope it helps. forums.autodesk.com/t5/AutoCAD-Map-3D/Rubber-Sheet-vector-files/… –  Dano May 5 '11 at 3:02
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.