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Alternative Coordinate Systems 319
Figure 21-18A
Spherical coordinates
in which the
angles and
represent the declination
and right
ascension, and
r represents the
radius or range.
fixed relative to the earth, rather than relative to the stars. This system is sometimes
used by aviators, military people, and meteorologists. Again, negative radii and nonstandard
angles are never used.
There’s a third alternative for spherical coordinates. The angle can represent the elevation
(the angle above or below the horizon), and can represent the azimuth, bearing,
or heading, measured clockwise from north. The radius or range r is, as in the other
Figure 21-18B
Spherical coordinates
in which the
angles and
represent the latitude
and longitude,
and r represents
the radius or
range.