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I know this is a frequent problem, I myself confronted with this problem many times, yet somehow each Autocad dataset I received is different (although they're from the same area). To some data, the projection I gave them worked perfectly, and in this case it didn't.

So, I've recently received some AutoCad data. Converted them in ArcMap. They are missing spatial reference. But I know their location. They're suppose to be in a specific city in Romania.

So first thing I did, I gave them the Stereo 70 projection (Romania's national projection), I assumed this is the projection they were created in, the data gets somewhere in the middle of the Mediterranean Sea. Second thing I tried is is giving them WGS84, and they got somewhere in the Atlantic Ocean ;)

PS: I use ArcGIS 10.1

PS2: I've tried all 3 conversion methods (I know) in ArcMap.

PS3: The autocad data came with no spatial reference. I only know they should be in a specific city.

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Are you sure that the autocad data had the correct coordinates in the first place? –  Devdatta Tengshe May 13 '13 at 8:52
    
the AutoCad data came with no spatial reference. –  Ligia May 13 '13 at 9:48
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AFAIK, AutoCAD files never come with Spatial reference. What they come with, are coordinates. Each point, line and other objects are at a specific coordinate. Sometimes, these coordinates are defined with a local reference point, sometimes they are arbitrary, and sometimes, they might be in a specific projection/ spatial-reference. –  Devdatta Tengshe May 13 '13 at 10:04
    
1. how can i make sure that the autocad data had the correct coordinates in the first place? –  Ligia May 13 '13 at 10:57
    
Open two or more Autocad files (DWG) in ArcMap. See if they align. If they do, then they have a consistent coordinate system. If they don't, then you need to correct them in the source CAD files. –  Devdatta Tengshe May 13 '13 at 11:13

1 Answer 1

up vote 2 down vote accepted

As you have mentioned in the comments, your old and new CAD files do not overlap, when imported in ArcGIS. This means, that they do not have a consistent coordinate system.

You could either correct them in AutoCAD, which is a better option, since their topology will be maintained, or you could import them into a geodatabase, and then use Spatial Adjustment to align the old data with the new data.

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Thank you very much with all the help. You were right the autocad data had wrong coordinates, and you helped me find out that. Unfortunately I don't have AutoCad, so I've tried Spatial Adjustment. It worked. Not perfectly, but it worked. Thanks a lot again. –  Ligia May 14 '13 at 6:07
    
Glad to help you out! –  Devdatta Tengshe May 14 '13 at 6:08

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