Custom Coordinate System

[cattjake]

Good afternoon,

I am having trouble figure out how to create a custom coordinate system. I am looking specifically at the local plane coordinates created for New York City by the U.S. Coast and Geodetic Survey; the Bogart grid. My current drawings are in the correct X and Y position for the Bogart system but have no Datum, no Projection associated to the drawing. I wanted to create a coordinate system for the Bogart system so that I could take shape files, which are in NY Staten Island NAD 83, and project them onto my existing work.

I know an approximate conversion for Bogart to New York Staten Island 27:

x = 1,988,023.75 - 0.99997339*W - 0.00135012*S

y = 157,512.4 + 0.00135012*W - 0.99997339*S

And the transformation from NW SI 27 to NY SI 83 should be within CAD.

My question is how do I create a custom coordinate system for the Bogart system so that I can set my drawing to it and thus project drawings from coordinate systems?