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I have converted a .dwg to a .shp using the CAD2SHP app. I made sure that there would not be a .prj file when I did the conversion. Defined projection once I opened up the file in Arc as a .shp. Then I bought in another .shp, with the same GCS and PCS. I don't see any differences between the two, and yet they will not line up.

Arc has not shown me any errors in the process of converting or projecting any of the data.

The only clue I can provide is that they have different coordinate values, one in the thousands and the other in the millions. In full extent they appear quite far apart.

Any insight - or a link to someone with a similar issue.

PolyGeo
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Edward Curran
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  • It sounds like your CAD file is in a local coordinate system or grid, is there a dgw file associated? if not you might need to georeference the CAD drawing. – Michael Stimson May 13 '18 at 22:51
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    This is one of the more common questions here. Yes, your initial coordinate reference assertion was incorrect. Rather than describing the difficulties with the incorrect reference in play, you should rewrite the question to focus on the errors you got initially. The only solution to the later errors is to fix the initial one.. – Vince May 13 '18 at 23:09
  • To answer the above, the CAD file is a dgw. The second comment I don't understand: I don't know what a "reference assertion" is, nor a "reference in play". It would be great to fix the initial error - this is why I've posted a question on GIS stack exchange in the first place. – Edward Curran May 13 '18 at 23:25
  • Don't forget to take the [Tour]. Near the beginning of your question you say "I tried ma[n]y times but got error messages that did not give me an idea of what was going on." The first of these is what I think you should focus your question on. An answer to that is likely to cause any subsequent issues to evaporate. – PolyGeo May 13 '18 at 23:31
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    Your CAD file is a DGN, a DGW is a world file https://en.wikipedia.org/wiki/World_file which describes the affine transformation from the CAD coordinate system into world units. It is very common for engineers, drafters and designers to prefer a local coordinate system, with an origin just outside the scope of works to keep the numbers very small, using a world file you can transform these units into GIS units. Have a read of http://desktop.arcgis.com/en/arcmap/10.3/manage-data/cad/about-georeferencing-cad-datasets.htm about georeferencing a CAD drawing. – Michael Stimson May 14 '18 at 01:04

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