This section describes the convention used to define azimuth and
elevation angles.

The *azimuth angle* of a vector is the angle between the
*x*-axis and its orthogonal projection onto the
*xy*-plane. The angle is positive when going from the
*x*-axis toward the *y*-axis. Azimuth angles lie between
–180° and 180° degrees, inclusive. The *elevation angle* is the angle
between the vector and its orthogonal projection onto the *xy*-plane. The
angle is positive when going toward the positive *z*-axis from the
*xy*-plane. Elevation angles lie between –90° and 90° degrees, inclusive.