Using a watch and the sun as a compass
An analog watch can be used to locate north and south. The Sun appears to move in
the sky over a 24 hour period while the hour hand of a 12-hour clock facetakes twelve hours to complete one rotation. In the
northern hemisphere, if the watch is rotated so that the hour hand points
toward the Sun, the point halfway between the hour hand and 12 o'clock will
indicate south. For this method to work in the southern hemisphere, the 12 is
pointed toward the Sun and the point halfway between the hour hand and 12
o'clock will indicate north. During daylight saving time, the same method can be
employed using 1 o'clock instead of 12.
The method depends on the assumption that the azimuth of the Sun changes at a constant rate during a day. Strictly, this
is true only when the observer is at one of the Earth's poles. Seen from moderately high latitudes,
say more than 50 degrees North or South, the Sun's azimuth changes at a rate
that is sufficiently constant to allow this method to be useful. Seen from
lower latitudes, the Sun's azimuth changes much more rapidly around noon than
at other times of day. In an extreme case, when the Sun passes directly
overhead at noon, its azimuth abruptly changes by 180 degrees, from due East to
due West. Obviously, this completely invalidates the use of a watch as a compass.
There are also relatively minor inaccuracies due to the difference between local time and zone time, and due to the equation of time.