How do I get my CAD data to project correctly without georeferencing?

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10-01-2020 01:23 PM
LaurenConnor
New Contributor II

Hi All,

Okay, so total newbie when it comes to working with .dwg files, but I am about to throw my computer out a window and would love some guidance!

I have received .dwg files with the land surveyor report that gives me the information about the coordinate datum as well as the 'equation' on how to convert state plane to project coordinates. 

First: Is that actually an equation? If not, what is the translation. 

Second: No matter what combination of numbers I try, I just simply can't get the polyline to display in the correct location (working with State Plane Colorado Central). 

I probably did a poor job explaining this but I am happy to dive into it further. Please send help! 🙂

Thank you!

#cad to gis conversion issues#arcgis for cad#cad data

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18 Replies
LaurenConnor
New Contributor II

Thanks for the extra suggestions Jessie, the CAD data is on a modified State plane (Colorado Central). I think my next step is changing the Easting and Northing to have everything line up correctly, but I just can't figure out those numbers. 

StephenHaney
New Contributor II

Lauren,

I am attempting the exact same thing today.  My .dwg files had no spatial reference when given to me. I went in, as stated earlier, added my known project feature class to a blank map and walked through ESRI's process of moving the the .dwg file to the project file location by changing (adding to) the false easting values. Note: Prior to this I had to open the data frames coordinate system tab and rename the projection file. Apparently if you don't do this it can cause issues.  So...after all that the .dwg file did not budge, so I am obviously missing a step. Thanks for throwing this out to the masses. Let's see what help is out there.

LaurenConnor
New Contributor II

Hi Stephen, 

I am sorry you are also going through this trouble, but I am also thankful I am not the only one. There has to be a way to figure this out, it should be something fairly simple since Arc and CAD are used in conjunction fairly often. Please let me know if you happen to figure it out!

Good Luck!

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StephenHaney
New Contributor II

Hey Lauren.  I was able to get my .dwg files to line up. Question, have you tried bringing in the .dwg file to a blank .mxd, THEN setting the data frames coordinate system?  As opposed to setting the properties prior to bringing in file.

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LaurenConnor
New Contributor II

I have (I think). Did your data just line up doing that? Curious if you had to mess with the easting and northing.

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

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StephenHaney
New Contributor II

I did not have to mess with the easting/northing at all.  For me, the secret was knowing what coordinate system the engineer set in AutoCad. My first go around with the data I was simply handed a dwg file and asked to bring it into our project map. That is what took me down the path of adjusting the easting/northing, which never really panned out.  

I have a question for you though.  When you first brought the original.dwg files into a blank .mxd did it state there was no spatial reference information?  If so, I "think" you want to get back to that point.  I say that because even when our engineer told me he applied a state plane coordinate system to the file, it still came in without any spatial reference; so ArcMap was not recognizing it. For me this said that as long as I set my data frame to a matching coordinate system the data should snap into place...which it did. 

Side note: I had to speak to a couple of engineers familiar with autocad to find one who knew how to apply a coordinate system within that software.  My point is if the process that worked for me does not work you consider contacting an autocad person to re-apply a cs and repeat the steps above.  Good luck.

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JessieSmucker
New Contributor III

Hi Lauren,

One more suggestion! If it's ending up in neighboring state, try changing the coordinate system from meters to feet or vise versa in the data frame. Could just be an issue of units.

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MelitaKennedy
Esri Notable Contributor

Hi Lauren, 

I'm very sorry for the late response. Can you post the equation/steps the surveyor gave you for the data? For CAD data it's sometimes possible to assign translation/rotation/scale values to a CAD layer. It's also sometimes possible to modify the projection parameters (scale factor, false easting, false northing) and create a custom coordinate system that gets the data to match up. I have two documents that discuss some of this. If you (or anyone else) sends me an email, I'll send them. They're pretty old now and written for ArcGIS Desktop so workflows may be different if you're using ArcGIS Pro.

Melita

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MelitaKennedy
Esri Notable Contributor

Duh! mkennedy at esri dot com

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