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donderdag, november 02, 2006

don't trust the sun

Of course it is possible to orienteer on almost any map, but it is much more enjoyable to use maps made specifically for orienteering.
Most of the characteristics of orienteering maps are related to those found on hiking and general use maps produced by the government. However, one feature of orienteering maps is specific our sport: the north lines. These are parallel lines drawn running from magnetic south to magnetic north, and are spaced 500 meters apart on the map.

Luckily north lines on orienteering maps aren't drawn pointing to true north. The angle between magnetic north and true north (the declination) varies widely in different parts of the world, and because orienteers use compasses to orient themselves (to magnetic north, not true north), it has become the standard to provide a series of reference lines on the map so that it is easy to use an orienteering compass to take a bearing.

Pasi Ikonen is one of the best orienteers who is running without a compass. But what happens if he would orienteer himself on the sun in Brazil?
The sun is in the geografical north at noon, But the north of the map isn't. This map gives the declination differences in the world.

For Brasil (Paraná): the location of the Military World Championships next week, we find a declination of 15°. In New Zeeland you can find a declination of 20-25° while moest of western Europe has a declination lower than 5°.

If we take an example for Brasil (Pinhao), declination 15°, what would be the deviation over 100m?

If you run 100m in wrong direction you would end up 26meters from the control . To correct this you have to run 26meters in 82,3 degrees (slightly backward ).

Conclusion: don't trust the sun.


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