The man page for pfMakePolarSeg contradicts itself with respect to
  the meaning of azimuth and elevation. The correct paragraph should
  be:

	pfMakePolarSeg sets dst to the segment which starts at pos and
	has length length and points in the direction specified by azi
	and elev.  azi specifies the azimuth (or heading), which is the
	angle which the projection of the segment in the X-Y plane
	makes with the +Y axis.  elev specifies the elevation (or
	pitch), the angle with respect to the X-Y plane.  The positive
	Y axis is azi=0 and elev=0.  Azimuth follows the right hand
	rule about the +Z azis, e.g. -  +90 degrees is the -X axis.
	Similarly, elevation follows the right hand rule about the X
	axis, e.g. -  +90 degrees is the +Z axis.

  Note that in IRIS Performer 1.0, an azi and elev of 0.0 is equivalent
  to the +X axis while in 1.1, this has been changed to the +Y axis.