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How to rotate a custom spatial reference (for a CAD file)

Question asked by housewren on Jan 6, 2015
Latest reply on Feb 13, 2015 by aaronch

I have an old CAD drawing of a building floorplan which has no known coordinate system.  I work in NAD_1983_CORS96_StatePlane_Michigan_South_FIPS_2113_Ft_Intl for my GIS, so I created a custom coordinate system based on that (had to change the units to inches and adjust the false northing and false easting) to get my CAD the right size and in more or less the right location.  However, the building is slightly rotated.  I applied a rotation angle on the CAD layer's Properties>Transformations.  Once I found the angle that would make the lines parallel, I again adjusted the false northing and false eastings in the custom projection so all the features would line up properly.  Is there any way to apply this rotation angle to the custom projection I already have?

 

I have the book "Lining Up Data" where it talks about creating a custom projection for a rotated file but my non-projected CAD is so far from the proper location that I can't detect the correct rotation until I apply a projection that shifts the CAD to the right area.  How can I create a custom projection that both shifts and rotates?

 

Here are my custom projection parameters:

NAD_1983_CORS96_SmithHall_custom_inch_5

Authority: Custom

 

Projection: Lambert_Conformal_Conic

False_Easting: 6504893.725401909

False_Northing: -2117372.591675

Central_Meridian: -84.36666666666666

Standard_Parallel_1: 42.1

Standard_Parallel_2: 43.66666666666666

Latitude_Of_Origin: 41.5

Linear Unit: Inch (0.0254)

 

Geographic Coordinate System: GCS_NAD_1983_CORS96

Angular Unit: Degree (0.0174532925199433)

Prime Meridian: Greenwich (0.0)

Datum: D_NAD_1983_CORS96

  Spheroid: GRS_1980

    Semimajor Axis: 6378137.0

    Semiminor Axis: 6356752.314140356

    Inverse Flattening: 298.257222101

 

and this is the angle that lines things up on the CAD Transformations tab: -0.788925

 

Thanks,

Cheryl

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