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Sunday, 5 April 2009

Thoughts on Topo Navigation

I was supposed to be out last night with a few of the top navigators from around the Wellington area practising some night navigation out the back of Eastbourne. I was really looking forward to getting out there at night time for the first time in a while. Unfortunately when I was putting checkpoints out on Thursday I managed to stand on the remains of an old stump and get a splinter square up through the ball of my foot. It broke off in there, but after I managed to wiggle my shoe off - which was now joined to my foot - Penny managed to pull it out while I gritted my teeth like I was about to get my leg amputated. It was first scene "Dances with Wolves" stuff. Ugly.

The map from 2008's Boohai Rogaine - Imagine it at night!!

But anyway, since I couldn't go out and practice I thought I would try and unpack how I navigate on topo maps at night, and how this differs from day time navigation. Some brief thoughts:

- At night the main sense you use for navigation - sight - is reduced. You have to focus on the navigational aids available in your circle of light. Those are: Map, Compass and Watch

- At night because it is hard to "read" the ground, it is far far harder to relocate. Hence it is worth navigating very "carefully". Note you are navigating carefully, not running slowly. As I have previously discussed on this blog, going slower than you usually would isn't the same as being careful!

- You are keeping the map orientated and using the compass often. A compass with an automatic declination adjustment is IDEAL to save you guesstimating the 20% when you are tired and in a hurry (only on maps not set to magnetic north). The guesstimation errors can mount up.

- So you have a plan, you are on your compass. Often in the absence of other features your "where am I on the ground" navigation is going to be limited to "after the fact" rather than "looking ahead". For example instead of in the day time knowing that you are at the bottom of a steep three contour slope, at night time you will only be certain of your location after you have climbed this slope. You need to consciously adjust your thought processes from..."is that..." to "was that...".

- Time. In the absence of wider visibility "time" stands out as a way to measure distance. As you travel around a course you should be able to get a feel for how long in different types of terrain it takes you to cover certain amounts of distance. Try it out alongside your usual navigation techniques to see how accurate you can become - sometime you might need it.

- Awareness of your own weaknesses and abilities. What challenges are there in finding a particular checkpoint? Can I expect to overcome them? What mistakes am I prone to making? Personally, with an orienteering background, I am inclined to slip out of scale. To fail to discard irrelavancies in the terrain that are not of the size to be represented on the map. Be aware of your weaknesses and work within your abilities!

The last and more practical solution comes from Adventure Racer Liam Drew "have a big ..... headlamp"! I have done a few races with Chris Forne, and also previously with Bruce McLeod. These guys are without a doubt two of the best navigators around, but they also seemed to have these massive lights. The ability to turn on the sun for a few seconds of so when you most need it cannot be underrated.

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