Chapter 11: Airport Operations  Figure 11-2.  Sectional chart and legend. The equator is an imaginary circle equidistant from the  poles of the Earth. Circles parallel to the equator (lines  running east and west) are parallels of latitude. They are  used to measure degrees of latitude north (N) or south  (S) of the equator. The angular distance from the  equator to the pole is one-fourth of a circle or 90°. The  48 conterminous states of the United States are located  between 25° and 49° N latitude. The arrows in Figure 11-3  labeled “Latitude” point to lines of latitude.  Meridians of longitude are drawn from the North Pole to  the South Pole and are at right angles to the Equator.  The “Prime Meridian,” which passes through Greenwich,  England, is used as the zero line from which measurements are made in degrees east (E) and west  (W) to 180°. The 48 conterminous states of the United  Remote Pilot – Small Unmanned Aircraft Systems Study Guide  68 Figure 11-3.  Meridians and parallels—the basis of  measuring time, distance, and direction. Latitude and Longitude (Meridians and Parallels) 