Copyright Goodheart-Willcox Co., Inc. Chapter 4 Understanding Three-Dimensional Coordinates and User Coordinate Systems 103 the current UCS to all viewports, enter the All option. See Chapter 5 for a complete discussion of model space viewports. Preset UCS Orientations AutoCAD has six preset orthographic UCSs that match the six standard ortho- graphic views. With the current UCS as the top view (plan), all other views are arranged as shown in Figure 4-30. These orientations can be selected by using the Named UCS Combo Control drop-down list in the Coordinates panel of the Home or Visualize tab in the ribbon, entering the command on the command line, or using the Orthographic UCSs tab of the UCS dialog box. When using the command line, type the name of the UCS (FRONT, BACK, RIGHT, etc.) at the fi rst prompt: Specify origin of UCS or [Face/NAmed/OBject/Previous/View/World/X/Y/Z/ZAxis] World: FRONT or FR↵ Note that there is no orthographic option listed for the command. The Relative to: drop-down list at the bottom of the Orthographic UCSs tab of the UCS dialog box specifi es whether each orthographic UCS is relative to a named UCS or absolute to the WCS. For example, suppose you have a saved UCS named Front Corner that is rotated 30° about the Y axis of the WCS. If you set current the top UCS relative to the WCS, the new UCS is perpendicular to the WCS, Figure 4-31A. However, if the top UCS is set current relative to the named UCS Front Corner, the new UCS is also rotated from the WCS, Figure 4-31B. The Z value, or depth, of a preset UCS can be changed in the Orthographic UCSs tab of the UCS dialog box. First, right-click on the name of the UCS you wish to change. Then, pick Depth from the shortcut menu, Figure 4-32A. This displays the Orthographic UCS Type UCS UCSMAN Top Bottom Front Back Left Right Figure 4-30. The standard orthographic UCSs coincide with the six basic orthographic views.