# need help with surveyor notes and adjusting CAD dwg coordinate system

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07-11-2011 06:16 AM
New Contributor
Hello,
I have several CAD dwg's that I have to bring into Arcmap (9.2).  All of them were using a local coordinate system.  I have the surveyor's notes that say it was based of of the Indiana state plane west by a factor of 0.9999586191...I have no idea how to adjust a coordinate system and I have tried anything I can think of to do so.  Any help is appreciated.
Thanks!
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5 Replies
Esri Notable Contributor
Hello,
I have several CAD dwg's that I have to bring into Arcmap (9.2).  All of them were using a local coordinate system.  I have the surveyor's notes that say it was based of of the Indiana state plane west by a factor of 0.9999586191...I have no idea how to adjust a coordinate system and I have tried anything I can think of to do so.  Any help is appreciated.
Thanks!

Hi,

One way is to use the CAD file's property page in ArcMap (not ArcCatalog). It should let you apply a scale factor.

Another way is to apply the scale factor to the Indiana West definition and create a custom coordinate system.

Assign the Indiana West definition to the CAD data. Now open the coordinate system definition and modify it. You'll have to figure out whether you need to apply this value directly or it's inverse. You want the value that will adjust the state plane coordinates TO the adjusted system.

You need to apply the SF to 3 projection parameter values:

false easting
false northing
scale factor

So if the combined scale factor is 0.9 (let's say) and the projection's scale factor is 0.9998, the new scale factor is 0.89982. Similarly, if the false easting is 100000, the new value is 90000.

Melita
New Contributor
I'm sorry, but I've never done any of that.

Is there a tutorial somewhere?  Where are you getting a combined scaled factor that needs to be put in with the factor given to me in the survey notes?

Hi,

One way is to use the CAD file's property page in ArcMap (not ArcCatalog). It should let you apply a scale factor.

Another way is to apply the scale factor to the Indiana West definition and create a custom coordinate system.

Assign the Indiana West definition to the CAD data. Now open the coordinate system definition and modify it. You'll have to figure out whether you need to apply this value directly or it's inverse. You want the value that will adjust the state plane coordinates TO the adjusted system.

You need to apply the SF to 3 projection parameter values:

false easting
false northing
scale factor

So if the combined scale factor is 0.9 (let's say) and the projection's scale factor is 0.9998, the new scale factor is 0.89982. Similarly, if the false easting is 100000, the new value is 90000.

Melita
New Contributor
Does anyone have any new suggestions?

Being somewhat new at using CAD Data, I don't know how to do what Ms. Kennedy said.
Thanks,
Amber
New Contributor III
Does anyone have any new suggestions?

Being somewhat new at using CAD Data, I don't know how to do what Ms. Kennedy said.
Thanks,
Amber

Hi Amber,

You can check here. Let me know if this doesn't help you out.
Esri Contributor
One alternative is to georeference the CAD file (graphically) to existing features in your data frame: