Coordinate Systems - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 86

UCS icons
In 3D, the UCS icon, represented by the three orthographic axes, is very important as
it tells us every instant which and where is the active UCS. Normally we work with a
3D icon, but a 2D icon is also available.
Identifying UCS icons
Depending on the situation and current visual style, the UCS icon can adopt different
aspects:
In 2D wireframe visual style, the icon is represented by lines. If the UCS icon has
a small square (as shown in image 1), it means that the world coordinate system is
current. Without the small square (as shown in image 2), it means it's a current user
coordinate system. With all visual styles, except 2D wireframe, the icon is shaded (as
shown in image 3) and there is no difference between the world coordinate system
and the user coordinate system. Particularly in 2D projects, we may opt for a 2D icon
(as shown in image 4) where the Z axis is absent and the world coordinate system is
indicated by the letter W .
Modifying the UCS icon
To display or modify the UCS icon, we can apply the UCSICON command. It has the
following options:
• ON/OFF : This turns the UCS icon visibility on or off in the current viewport.
• All : This will apply visibility and origin settings to all viewports.
• Noorigin/ORigin : This displays the icon at the coordinate system origin if
the origin is visible in the current viewport. If the origin is not visible, it is
displayed at the lower-left corner.