Magnetic Declination GODZone N Z

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Magnetic declination is a big factor to consider when navigating in New Zealand. For those who are not aware of the phenomenon, it simply means that your compass (that handy little tool invented by the Chinese over two thousand years ago) and map do not ‘point’ in the same direction – or, to put it another way, the north on your map is somewhere between 20 and 25 degrees out from the north of your compass.

Rather than try to remember how to adjust for this difference and make yourself weep with the confusing nature of it all, go for this easy option:

Pick a square at the top middle of your map and mark a circle around the junction of the Northings and Eastings line. Count 4 squares to the right (East) and mark an ‘X’ on the junction of lines. Go back to the circle and then count 10 squares down (South) and mark another X. Take a fine red pen (to avoid confusion on the map) and draw a straight line that bisects both the X’s on the map. Move the ruler so that the other side runs parallel with the new line and draw another. Repeat until have a useful number on your map.

When you take your bearings (this should be your back up navigators main job when checking) just use the red lines rather than the black ones. The beauty of this method is that it gives a line of just about spot on 22 degrees and can be used on any map scale as long as the squares are actually square shaped.

Is it worth the effort? Well, if you look at the example map you can see that the team who walks just over 10km on the unadjusted bearing at GODZone can expect to be 4km out from their target. Which equates, on average, to about 2hrs of lost time for novice teams on the trekking stages. We think the investment in a sparkly new pen and ruler are well worth it. Heck, get yourself a fluffy pencil case whilst you’re at it. Put them on the Christmas list along with the insoles.

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