About the User Coordinate System (UCS)

The user coordinate system (UCS) is a movable coordinate system, which is a fundamental tool both for 2D drawing and 3D modeling.

The UCS defines

• The XY plane, also called the work plane, on which objects are created and modified
• The horizontal and vertical directions used for features like Ortho mode, polar tracking, and object snap tracking
• The alignment and angle of the grid, hatch patterns, text, and dimension objects
• The origin and orientation for coordinate entry and absolute reference angles
• For 3D operations, the orientation of work planes, projection planes, and the Z axis for vertical direction and axis of rotation

You can change the location and orientation of the current UCS by clicking the UCS icon and using its grips, or with the UCS command. Display options for the UCS icon are available with the UCSICON command.

The UCS in Paper Space

You can move and rotate the UCS in paper space on a layout; however, the UCS in paper space is restricted to 2D operations.

Understand the World Coordinate System (WCS)

All objects in a drawing are defined by their coordinates in the World Coordinate System (WCS), which cannot be moved or rotated. The WCS and the UCS are initially coincident in new drawings.