UCS Command

Manages user coordinate systems

	Standard toolbar:
	Tools menu: UCS
	Command line: ucs

Origin / ZAxis / 3point / OBject / View / X / Y / Z / Prev / Restore / Save / Del / ? / <World>: Enter an option or press ENTER

The user coordinate system is a movable system for coordinate entry, planes of operation, and viewing. Most AutoCAD LT geometric editing commands are dependent on the location and orientation of the UCS.

The UCS command sets the orientation of the user coordinate system in 3D space. It defines the orientation for 2D objects for the THICKNESS command. It also provides the axis of rotation for the ROTATE command and the default projection plane for specifying points.

World (UCS)

Sets the current UCS to the World Coordinate System (WCS). The WCS is the basis for all user coordinate systems and cannot be redefined.

Origin (UCS)

Defines a new UCS by shifting the origin of the current UCS, but leaving the direction of its X, Y, and Z axes unchanged.

Origin point <0,0,0>: Specify a point

Specify a new origin point relative to the origin of the current UCS. If you do not specify a Z coordinate value for the origin, this option uses the current elevation.

Zaxis (UCS)

Defines a UCS with a particular positive Z axis.

Origin point <0,0,0>: Specify a point
Point on positive portion of Z-axis <current>: Specify a point

Specify a new origin and a point that lies on the new positive Z axis. The Z Axis option tilts the XY plane.

3point (UCS)

Specifies the new UCS origin and the direction of its positive X and Y axes. The Z axis follows by applying the right-hand rule. You can use this option to specify any possible coordinate system.

Origin point <0,0,0>: Specify a point (1)
Point on positive portion of the X-axis <current>: Specify a point (2)
Point on positive-Y portion of the UCS XY plane <current>: Specify a point (3)

The first point specifies the origin of the new UCS. The second point defines the positive X axis. The third point defines the positive Y axis. The third point can be anywhere on the positive Y portion of the new UCS XY plane.

Object (UCS)

Defines a new coordinate system based on a selected object. The new UCS has the same extrusion direction (positive Z axis) as that of the selected object.

Select object to align UCS: Select an object

The following objects cannot be used: polyline, viewport, spline, ellipse, ray, xline, leader, mtext.

For objects other than 3D faces (available only when viewing AutoCAD LT drawings), the XY plane of the new UCS is parallel to the XY plane in effect when the object was drawn. However, the X and Y axes can be rotated differently.

The new UCS is defined as described in the following table.

Object Method of UCS determination

Arc The center of the arc becomes the new UCS origin. The X axis passes through the arc endpoint that is closest to the selection point.

Circle The center of the circle becomes the new UCS origin. The X axis passes through the selection point.

Dimension The midpoint of the dimension text becomes the new UCS origin. The direction of the new X axis is parallel to the X axis of the UCS in effect when the dimension was drawn.

Line The endpoint nearest the selection point becomes the new UCS origin. AutoCAD LT chooses the new X axis so that the line lies in the XZ plane of the new UCS. The line's second endpoint has a Y coordinate of zero in the new system.

Point The point becomes the new UCS origin.

2D polyline The start point of the polyline is the new UCS origin. The X axis extends along the line segment from the start point to the next vertex.

2D Solid The first point of the solid determines the new UCS origin. The new X axis lies along the line between the first two points.

Shape, Text,
Block Reference,
Attribute Definition The insertion point of the object becomes the new UCS origin, and the new X axis is defined by the rotation of the object around its extrusion direction. The object you select to establish a new UCS has a rotation angle of zero in the new UCS.

View (UCS)

Establishes a new coordinate system with the XY plane perpendicular to your viewing direction (parallel to your screen). The UCS origin remains unchanged.

X / Y / Z (UCS)

Rotates the current UCS about a specified axis.

Rotation angle about n axis <0>: Specify an angle

In the prompt, n is X, Y, or Z. Enter a positive or negative angle to rotate the UCS. AutoCAD LT uses the right-hand rule to determine the positive direction of rotation around the axis.

You can define any UCS by specifying an origin and one or more rotations around the X, Y, or Z axis.

Prev (UCS)

Restores the previous UCS. AutoCAD LT saves the last 10 coordinate systems created in paper space and the last 10 coordinate systems created in model space. Repeating the Previous option steps back through one set or the other depending on which space is current.

Restore (UCS)

Makes a saved UCS the current UCS. Restoring a saved UCS does not reestablish the viewing direction in effect when the UCS was saved.

? / Name of UCS to restore: Enter ? or a name

Enter ? to view a list of names.

UCS name(s) to list <*>: Enter a wild-card pattern or press ENTER

Save (UCS)

Saves the current UCS to a specified name. The name can contain up to 31 characters, including letters, digits, and the special characters dollar sign ($), hyphen (-), and underscore (_). AutoCAD LT converts all UCS names to uppercase.

? / Desired UCS name: Enter ? or a name

Enter ? to list the currently defined UCS names.

UCS name(s) to list <*>: Enter a wild-card pattern or press ENTER

Del (UCS)

Removes the specified UCS from the list of saved coordinate systems.

UCS name(s) to delete <none>: Enter a name or a list of names separated by commas

? List (UCS)

Lists defined UCS names and provides the origin and X, Y, and Z axes for each saved coordinate system relative to the current UCS. If the current UCS is unnamed, it is listed as *WORLD* or *NO NAME*, depending on whether it's the same as the WCS.

UCS name(s) to list <*>: Enter a wild-card pattern or press ENTER

Changing from one UCS to another does not change the drawing view unless the UCSFOLLOW system variable is on.

Related Commands: DDUCS renames, restores, deletes, or lists defined coordinate systems. DDUCSP selects a preset User Coordinate System. PLAN displays the plan view of a specified UCS.
System Variables: UCSICON controls visibility and placement of the UCS icon in viewports. UCSNAME displays the name of the current coordinate system. UCSORG displays the origin point of the current coordinate system for the current space. UCSXDIR displays the X direction of the current UCS for the current space. UCSYDIR displays the Y direction of the current UCS for the current space.

Object	Method of UCS determination
Arc	The center of the arc becomes the new UCS origin. The X axis passes through the arc endpoint that is closest to the selection point.
Circle	The center of the circle becomes the new UCS origin. The X axis passes through the selection point.
Dimension	The midpoint of the dimension text becomes the new UCS origin. The direction of the new X axis is parallel to the X axis of the UCS in effect when the dimension was drawn.
Line	The endpoint nearest the selection point becomes the new UCS origin. AutoCAD LT chooses the new X axis so that the line lies in the XZ plane of the new UCS. The line's second endpoint has a Y coordinate of zero in the new system.
Point	The point becomes the new UCS origin.
2D polyline	The start point of the polyline is the new UCS origin. The X axis extends along the line segment from the start point to the next vertex.
2D Solid	The first point of the solid determines the new UCS origin. The new X axis lies along the line between the first two points.
Shape, Text, Block Reference, Attribute Definition	The insertion point of the object becomes the new UCS origin, and the new X axis is defined by the rotation of the object around its extrusion direction. The object you select to establish a new UCS has a rotation angle of zero in the new UCS.