To Create a Datum Csys
1. Click Create > Datum Csys. The COORDINATE SYSTEM dialog box opens and the References collector in the COORDINATE SYSTEM dialog box is activated.
2. Select a reference in the graphics window such as a datum plane, edge, coordinate system, or point to place the coordinate system.
To add more references, hold down the CTRL key and select the required references in the graphics window.
If the selected references are not sufficient to create the coordinate system, you must select additional references until the coordinate system is fully constrained.
3. If you select a coordinate system as the reference, you can specify the Offset type. Select one of the following offset types on the Origin tabbed page:
Cartesian—Enter values for X, Y, and Z.
Cylindrical—Enter values for  Radius, Theta, and Z.
Spherical—Enter values for Radius, Theta, and Phi.
From File—Allows you to import a coordinate system's location from a transformation (.trf) file.
4. To adjust the offset distance, drag the coordinate system's handle in the graphics window to the desired location. Alternatively, enter the values for offset translation in the corresponding boxes. For example, if you set the offset type to Cartesian, enter values for X, Y, and Z.
5. Click OK in the COORDINATE SYSTEM dialog box to create the coordinate system. The coordinate system appears in the graphics window and also appears as a separate node on the GTS Tree.