Copyright Goodheart-Willcox Co., Inc. Chapter 4 Understanding Three-Dimensional Coordinates and User Coordinate Systems 83 Like spherical coordinates, cylindrical coordinates can also be entered as rela- tive coordinates. For example, a point drawn with the relative cylindrical coordinate @1.530,4 is located 1.5 units from the last point, at an angle of 30° in the XY plane of the previous point, and at a distance of four units up from the XY plane of the previous point. NOTE NOTE Turn off dynamic input before entering cylindrical coordinates. Dynamic input does not correctly interpret the entry when cylindrical coordinates are typed. Using Cylindrical Coordinates Using Cylindrical Coordinates Cylindrical coordinates work well for attaching new objects to a cylindrical shape. An example of this is specifying coordinates for a pipe that must be attached to an existing pipe, tank, or vessel. In Figure 4-5, a pipe must be attached to a 12′ diameter tank at a 30° angle from horizontal and 2′-6″ above the fl oor. In order to draw the pipe properly as a cylinder, you will have to change the UCS, which you will learn how to do later in this chapter. An attachment point for the pipe can be drawn using the POINT command and cylindrical coordinates. First, set the drawing units to archi- tectural. This can be done by selecting Drawing Utilities Units from the Application Menu and specifying the length units as Architectural in the Drawing Units dialog box. Next, set the PDMODE system variable to 3. Enter the POINT command and continue as follows: Current point modes: PDMODE=3 PDSIZE=0'-0" Specify a point: FROM↵ Base point: CEN↵ of (pick the base of the cylinder) Offset: @6'30,2'6"↵ (The radius of the tank is 6′.) The point can now be used as the center of the pipe (cylinder), Figure 4-5B. However, if you draw the pipe now, it will be parallel to the tank (large cylinder). By changing the UCS, as shown in Figure 4-5C, the pipe can be correctly drawn. You will learn how to do this later in this chapter. UCS is moved and rotated to this location @6′30, 2′6″ 30° A B C +Y –Y –X +X Figure 4-5. A—A plan view of a tank shows the angle of the pipe attachment. B—A 3D view from the southeast quadrant shows the pipe attachment point located with cylindrical coordinates. C—By creating a new UCS, the pipe can be drawn as a cylinder and correctly located without editing.