In order to determine your position on a map, you can make use
of a minimum of two fixed points relative to your position, say
trigonometric beacons or other landmarks, take a bearing on them
and triangulate back to your current location.
However, if you don’t have fixed landmarks, such as when you are
out on open seas, you have to make use of relative markers, such as
the sun and the stars. These tend to move relative to your
position, so it is vital that you determine their exact position
above the horizon at a given time; thus accurate timing is the key
to accurate position locating. Therefore, in the days before radio
and satellite communications a sailor’s navigational tools were the
sextant and an accurate and reliable chronometer or timepiece. A
wonderfully fascinating and entertaining book on this subject is
Longitude: The True Story of a Lone Genius who Solved the
Greatest Scientific Problem of his Time by Dava Sobel. If you
are interested in how latitude and longitude are determined using a
sextant and chronometer, the following website by Dr David
P Stern is useful.
Cape Town’s noon gun allowed the ships in the harbour to reset
their chronometers accurately. The tradition of firing a noon gun
dates back to 1806 when it was first fired from the Imhoff Battery
at the Castle. The cannons were moved to the current location in
1902. The two cannons are the oldest still in daily use in the
world, and have fired over 62 000 times. One cannon is on standby
in case the other misfires, and they are fired alternately on
alternate days, Monday through Saturday. The timing is done from
the Observatory and relies on an atomic clock to fire at precisely
noon. Because sound travels at about 330 m/s, the smoke cloud, and
not the big bang, is the indicator of precisely midday.
Now we have it so easy with GPS. Incidentally, your GPSr which
can determine your position anywhere on earth to within a few
metres also relies on very accurate timing (derived from atomic
clocks), and the stars have been replaced with satellites.
There are two routes you can choose to get to the Lion
Battery:
You can drive up from the city via the Bo-Kaap. Turn off
Buitengragt Street into Bloem Street and follow the Noon Gun sign,
making your way into Whitford Street, which then becomes Military
Road as it winds its way for about 1.2 km up Signal Hill. There is
parking on the premises. You could also cycle up via the same
route, but don’t cycle around on the grass once you are at the
battery – there are nasty large thorns which will puncture your
bicycle’s tyres, believe me: been there, done that!
If you prefer a nice little walk, drive to the top of Kloof Nek
and then turn off onto Signal Hill Road. You can park in the
parking lot at the end of Signal Hill Road, take the footpath
behind the toilets towards the radio mast and then walk back down
to the road you have just come on to a fairly steep jeep track
which starts at S 33° 55.041, E 18° 24.260. The vegetation along
the jeep track is not very interesting, but the views over Green
Point and the Waterfront after about ten minutes of strolling are
magnificent. Follow the track until you see a footpath leading off
north to the battery. When you reach the fence you can follow it to
the left to a gate which seems to be left open permanently. If you
follow the fence to the right it will take you to the entrance you
would reach by car as on the first route.
The cache container is a grey lunchbox-type, about 13cm x 14cm x
7cm. Please conceal it carefully again so that it is not visible
from either side of its hiding spot. Please also note, the cache is
NOT hidden in the dry-packed stone walls in the area.