The coordinates posted will take you to the entrance road of the
Illovo River Park. It is a popular spot to have a picnic and
to do some fishing in the lagoon. You will ultimately be able
to drive right up to the cache but you will have to solve the
navigation problem below to determine the final coordinates:
If you struggle to view the digits in the image as displayed,
please print out the image or click on one of the images posted in
the log of 20 June 2008 below.
Triangle ABC is an equilateral triangle and the cache is located
at the Centroid. The distances between AB BC and CA are
small. It is therefore not necessary to use spherical
trigonometry to calculate the coordinates of D.
When large distances are involved, calculating bearings,
coordinates and distances between waypoints is actually quite
complex. Due to the fact that the earth is not flat, but spherical,
normal trigonometry cannot be used. Rather, a special form of
trigonometry known as spherical trigonometry is used.
Prior to 1761, navigation was extremely difficult as longitude
could not be determined with any kind of precision. Navigators
could only make guesses which were usually inaccurate by many
hundreds of kilometers, beacause the technology had not yet been
developed to allow them to do the job properly.
Latitude did not pose a problem as it could be worked out by means
of angular measurements of the sun and stars taken with relatively
simple instruments.
To establish longitude, an instrument was needed that could keep
the time at the place of departure with perfect accuracy during
long sea journeys despite the motion of the ship. A chronometer
(watch) capable of keeping time to within three seconds per day was
needed.
It was not until 1761 that English clockmaker John Harrison was
able to meet this standard with his elegant Chronometer No 4.
Today, we not only have accurate timepieces but we are also
priveledged to have GPS which makes accurate navigation accessible
to a very wide audience and has made Geocaching a reality!
THE CACHE IS WELL HIDDEN. PLEASE EXTRACT CAREFULLY AND
PLACE BACK EXACTLY AS FOUND.
You can check your answers for this puzzle on
Geochecker.com.