Natural Navigation in the Southern Hemisphere
Using the sun, stars and moon to navigate in the northern hemisphere for many of us is now second nature, but our recent trip to South Africa gave me the chance to try out natural navigation techniques in the southern hemisphere which really got the old grey matter working.
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Starting with the stars. We are spoilt in northern latitudes by having a star directly above the northern rotational axis of the earth i.e. the pole star or Polaris. Below the equator things are a little bit more complicated as there is no equivalent star above the southern rotational axis of the earth, instead you have to locate position in a virtually starless part of the sky which is above this axis and this is done using the Southern Cross or the constellation Crux.
Made up of 4 bright stars and one slightly dimmer one it is one of the smallest of the modern constellations. It lies in the southern part of the milky way, almost exactly opposite Cassiopeia so if you are on the equator only one will ever be visible. There are a couple of different ways of using Crux to find south. Firstly draw an imaginary line between Acrux and Gacrux along the long axis of Crux and extend it past Acrux 4.5 times its length. The other way is to repeat this and then draw a line between the Southern Pointers; Alpha and Beta Centauri (or Rigil Kent and Hadar). Find the mid-point of this line and then take a line out from this at 90 degrees to intersect the line extending out from the Crux. We said things were more complicated in the southern hemisphere! Click on illustration below.
To confuse matters there is a constellation also in the southern milky way that rises before Crux that resembles it, so confirm it is Crux with the Southern Pointers. Below about 34 degress south the Southern Cross is visible all year round but above this it drop below the horizon during the southern hemisphere’s winter months.
Using the sun to navigate in the Southern Hemisphere is relatively straight forward and not dissimilar to using it in northern latitudes with a few subtle changes. To help understand the differences it is worth explaining the movement of the sun in the sky at latitudes more than 23.5 degrees south. From the spin of the earth the sun still rises in the east and sets in the west, however in the middle of the day it will now be to the north. This means that when using a shadow stick in the southern hemisphere the shortest shadow, i.e. when the sun is at its highest, will now point south. Apart from this it works in the same way.
To use an analogue watch in the southern hemisphere the method is similar to here, except instead of pointing the hour hand at the sun you point the 12 o’clock at the sun and then half the angle between this and the hour hand to give you your north/south line.
To use the moon one needs to remember that the side of the moon that grows as it waxes and then thins as it wanes is opposite so in the southern hemisphere a waxing moon grows from the left hand side not the right as it does in the UK. To use the moon to determine direction is too detailed to describe in this blog, but there is a method where you estimate the number of days the moon is in to the lunar cycle and then multiply that by the daily lag between the moon and the sun (12.2 degrees) and then from knowing where the sun is at a certain time you can calculate the direction of the moon reasonably accurately. This method still works in the southern hemisphere but the lag to the sun moves clockwise around the compass instead of anti-clockwise…………..I know of at least two people who will now be having a nosebleed!
Perhaps a simpler way of using the moon is when it is as a crescent (either waxing or waning). Drawing a line across the “horns” of the crescent and extending it down to the horizon will give you a reasonably good north bearing. If a moon is bright enough you can also do a shadow stick with the moon. Again the shortest shadow will point south.
Woodland Ways: Natural Navigation in the Southern Hemisphere | Bushcraft UK | Foraging Courses | Outdoor Bushcraft Skills