Copyright Goodheart-Willcox Co., Inc. 80 AutoCAD and Its Applications—Advanced When entering spherical coordinates, the longitude measurement is expressed as the angle in the XY plane and the latitude measurement is expressed as the angle from the XY plane. See Figure 4-1B. A distance from the origin is also provided. The coordi- nates represent a measurement from the equator toward either the North or South Pole on Earth’s surface. The following spherical coordinate entry is shown in Figure 4-1B. 7.53555 This coordinate represents an absolute spherical coordinate, which is measured from the origin of the current UCS. Spherical coordinates can also be entered as relative coordinates. For example, a point drawn with the relative spherical coordinate @23545 is located two units from the last point, at an angle of 35° in the XY plane, and at a 45° angle from the XY plane. If dynamic input is turned on, the “second” or “next” coordinate entry is automat- ically a relative entry (by default). The @ symbol is not entered. To enter absolute coor- dinates with dynamic input turned on, enter an asterisk (*) before the fi rst coordinate. PROFESSIONAL TIP PROFESSIONAL TIP Spherical coordinates are useful for locating features on a spherical surface. For example, they can be used to specify the location of a hole drilled into a sphere or a feature located from a specifi c point on a sphere. If you are working on such a spherical object, you might consider locating a UCS at the center of the sphere, then creating several different user coordinate systems rotated at different angles on the surface of the sphere. Any time a location is required, spherical coordinates can be used. Working with UCSs is introduced later in this chapter. Using Spherical Coordinates Using Spherical Coordinates Spherical coordinates are well suited for locating points on the surface of a sphere. In this section, you will draw a solid sphere and then locate a second solid sphere with its center on the surface of the fi rst sphere. Figure 4-1. A—Lines of longitude, representing the highlighted latitudinal segments in the illustration, run from north to south. Lines of latitude, representing the highlighted longitudinal segments, run from east to west. B—Spherical coordinates require a distance, an angle in the XY plane, and an angle from the XY plane. Lines of longitude (latitudinal segments) Lines of latitude (longitudinal segments) Distance 7.53555 Angle from the XY plane (latitude measurement) Angle in the XY plane (longitude measurement) A B