The user coordinate system (UCS) establishes the location and orientation of a movable Cartesian coordinate system. The UCS is an essential tool for many precision operations.
The UCS defines
- 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
By default, the UCS icon appears in the lower-left corner of the drawing area for the current model viewport. The UCS in each paper space layout is displayed as a drawing triangle.
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. By default, the UCS icon appears in the lower-left corner of the layout. You can change its default location with the UCSICON command.
Understand the World Coordinate System (WCS)
All objects in a drawing are defined by their coordinates in the World Coordinate System (WCS), a permanently fixed Cartesian coordinate system. The UCS is initially coincident with the WCS in new drawings. The squares in the lower-left corners of each of the icons indicates that the UCS icon is currently coincident with the WCS.