A compass can be useful to use alongside your map to help you orientate your map and yourself and to take a bearing so you know which direction to head. Extremely useful if you are travelling through thick bush, fog or at night where you can’t see features on the map. A compass has a magnetised needle that always points in the direction of magnetic north (usually about 23 degrees east of grid north). For an accurate reading you need to hold the compass flat and keep it away from metal objects that will affect the reading such as mobile phones and bike frames!
A baseplate compass (which is what we’ll talk about) has a bezel that can be rotated around the needle so you can measure and follow a bearing from it. This is very useful to use in conjunction with your map to work out which direction you need to go to get to your destination.
The compass needle is magnetised so will always point to magnetic north which is different to the grid north lines on a Topo map (which line up with the North and South poles). This difference is called the magnetic declination. In NZ, magnetic north is about 23 degrees to the east (right) of grid north (lines on your map). This can vary slightly depending on where in NZ you are (North or South Island) and changes gradually over the years. Magnetic declination often trips teams up in an adventure race but is actually quite straight forward once practised a few times.
One method I like to use and teach is to draw the magnetic north lines on your race map to avoid confusion or forgetting while you are racing.
- Use your compass to set the 23 degree angle (or whatever the declination states on your map) for magnetic north. Check it against the diagram on the map legend.
- Line up the orienting lines on the compass bezel with the grid north lines on the map.
- Use a ruler against the side of your compass to draw magnetic north lines across your map. They should be 23 degrees to the right of your grid north lines.
– Now you can use these new lines instead of the maps grid north lines and your compass reading will be accurate.
Taking a Bearing
- Line up one of the long edges of the compass from where you are to where you want to go, making sure the direction of travel arrow on the compass is pointing to where you want to go.
- Rotate the bezel until the orienting lines on your compass are pointing north in line with your new magnetic north lines on your map.
- Rotate yourself (and compass) until the red magnetic compass arrow is aligned with the orienting lines on the bezel. This is the direction you will travel in to find your destination.
It might sound confusing but will make a lot more sense once practised a few times. So grab compass and Topo map of your local area, get outside and start challenging yourself to accurately get from one point to the next using the above steps. Don’t wait until a few weeks before your race, the more you practise the more relaxed you will be going in to your race.
Kym is a mum of 3 boys, 5, 8 and 10 yrs, trains and races in multisport and adventure racing events and is very passionate about nutrition and wellness. She is the co-creator and retreat leader at NZ Adventure Retreats and is part of the team that has won the Spirited Women Adventure Race long course for the past 4 years.
Kym along with Rach Smith from Navigation North and Nic Leary (elite mountain biker and physio) will be running a specific Womens Adventure Race Skills weekend in Kapiti September 7th and 8th, Tauranga November 2nd and 3rd and Hawkes Bay Feb 29th and March 1st to help with up-skilling in different aspects of the race and helping you become a more confident and competent adventure racer. Contact firstname.lastname@example.org