Using the Units and Zone tab of the Drawing Settings dialog box, you can select linear and angular units, a coordinate system, and scale for the drawing.
Coordinates in AutoCAD Civil 3D are expressed using northings and eastings.
The AutoCAD Civil 3D coordinate system is always relative to the AutoCAD World Coordinate System (WCS). Northing is equivalent to AutoCAD Y and easting is equivalent to AutoCAD X.
AutoCAD Civil 3D object data is always presented in AutoCAD World Coordinate System coordinates. For example, the alignment data in the Alignment Entities vista in the Panorama window is listed in world coordinates. In addition, the AutoCAD Civil 3D transparent commands are based on the AutoCAD World Coordinate System. However, when you create an object and have an AutoCAD User Coordinate System (UCS) defined, the UCS is honored when you specify locations, which means that an insertion point or a coordinate is interpreted relative to the UCS.
AutoCAD Civil 3D objects are not aligned with the UCS. For example, labels can be oriented relative either to the current view, the World Coordinate System, or the labeled object, depending on the Orientation Reference setting, but they cannot be oriented to the UCS.
Similarly, objects, such as profiles, sections, and tables, cannot be oriented to the current UCS.
For more information about AutoCAD World Coordinate Systems and AutoCAD User Coordinate Systems, see the AutoCAD Help.