Greenwich, England, has a longitude of $0^\circ$ and an approximate latitude of $51.5^\circ$ N. If $R_{E}=3960$ miles is used for the radius of the Earth and degrees are used to measure angles instead of radians, then the spherical coordinates for Greenwich, England, are $(3960,0^{\circ},38.5^\circ )$. See Figure 62(b), where the angle $ECG=51.5^\circ$.