Magnetic declination is the basic principle of knowing when to navigate through the wilderness through maps and compasses.
However, using the addition/subtraction method, at least in the traditional way of teaching it, is a tricky thing. Just when you think you have got it, the concept will emerge, just like the fog in the morning light.
When finding a bearing, there is a simple and practical way to adjust the magnetic declination. The whole explanation begins with the definition of "north". '
There are two north
Many people know that there are two norths in terms of maps and compasses. The map shows true north, or the geographic north pole where all longitude lines intersect. The earth rotates around an imaginary axis that passes through the north and south poles.
The compass needle points to the magnetic north, and the magnetic north pole is determined by the earth's magnetic field. The location of Magnetic North moves over time, about 5 miles per hour. Now, it is slowly smashing in the northwestern part of Hudson Bay, Canada, about 450 miles north of the true north.
Magnetic declination
The angular difference between True North and Magnetic North is called "declination" or "change" in the aviation industry. The recession in different parts of the world is different. In Washington State, the reduction angle is 20° east. This means that Magnetic North is 20° east of Zhengbei. In Tennessee, the angle of reduction is 0°, while in Maine, the angle of reduction is 20°.
The deviation value can be found in the margin or legend of the topographic map. Because the magnetic north point is constantly moving, a recent topographic map can find your path in the woods.
It is worth remembering that the compass was calibrated for different parts of the world. So when you buy a compass, make sure it works for your big hiking holiday.
How to find your bearing
Please follow the steps below to find your location:
1. Place the compass on the map and the arrow on the bottom plate points in the direction you want.
2. Turn the dial face of the compass so that the north on the compass is parallel to the north on the map.
3. Place the compass horizontally in the palm of your hand and turn yourself until the pointer in the compass aligns with the northern marker on the face dial.
4. The large arrow on the bottom plate is now aligned with the bearing.
Deviation values and bearings - the trick to keep it going
If you walk 10 miles through the woods of Washington State, without considering the drop in your bearing, you will complete the goal of more than 3 miles. That's too much!
To avoid confusion about finding bearings, keep in mind the central principles:
Making map bearings = magnetic bearings.
You can achieve this by enabling you to compensate for the magnetic declination by adjusting the bearings. There are two ways to interpret the magnetic declination when looking for bearings: adjustable compasses and compasses that are not adjustable.
The easiest way is to use an adjustable compass. Simply rotate the declination adjustment screw on the compass to the correct value and all readings will automatically be converted to true north. If it is available, it is best to use an adjustable compass while walking.
The next best way to explain declination is to mark the reduction on the unadjustable compass at the beginning of the journey.
this is very simple. For example, when the local map indicates a west value of 20°, you mark the compass dial as 340°. If the map indicates a 10° reduction to the east, you mark the compass as 10°. Make a mark with a permanent mark and then erase with alcohol.
Now, when you are taking the bearing on site, place the compass horizontally in the palm of your hand and turn yourself until the pointer in the compass aligns with the reduced mark on the face dial. The large arrow on the bottom plate then points to the bearing and automatically compensates for the magnetic declination.
Orignal From: True Arctic and magnetic decay - the trick to keep it going
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