The directional reference shows which way is north, south, east and west on a map. Commonly, this is done using a "north arrow". Find the north arrow near the bottom of your Cumberland map. There are three different "norths" shown on this map. The arrow in the middle, shown pointing to the star, is the True North. The star on the map represents a real star called Polaris, often referred to as the North Star. Polaris appears in the night sky directly over the North Pole. This point is where the earth's imaginary axis of rotation reaches the surface and is called True North, or Geographic North. Because you can see Polaris from the entire northern hemisphere, the North Star has been used by navigators to determine direction for thousands of years.
The arrow to the left, marked as MN, is the magnetic north. This is the direction that the needle on a magnetic compass will point. The magnetic north of the earth is not the same as the true north. The earth's magnetic north pole only happens to be in the same general location as the True North. The magnetic north Pole is actually in northern Canada, and, to make things even more confusing, it slowly moves around over time. Although not exactly in the same place, since the magnetic north and true north are more or less in the same location we can use a magnetic compass to determine direction. The invention of the compass by the Chinese was a great aid to navigation because directions could now be determined when you couldn't see the North Star, such as during the day or when it was overcast. However, when navigating using a compass, you must be sure to realize that there is a difference between True North, indicating the direction you actually want to go,
and Magnetic North, the direction that your compass is pointing. The difference between the two is called the magnetic declination, which is the angle between the two arrows shown on the map. This angle will vary depending on your location on the earth. In Cumberland, the magnetic declination is 9.5 degrees.
The third type of north on the map, that indicated by the middle arrow is the Universal Trans-Mercator grid north. The UTM grid is a system for locating points on the earth's surface. We will not cover UTM in this class, so ignore it.
Looking at the north arrow on the bottom of your map, you will see that it points to the top of the map. Traditionally, cartographers put north at the top. This has not always been true, many old maps put south at the top. With north at the top of the map, south will be on the bottom, east to the right and west to the left. North does not have to be at the top, though, and on some maps, it cannot possibly be. Consider, where is north on a map of Antarctica? North is at all of the edges of the map.
The Compass and Azimuth
The use of directions on the map is helpful in the location of one place in relationship to another place. Given a starting point, knowing the direction and distance to another point is sufficient to locate it. You are probably familiar with at least 8 compass directions, but the illustration below shows you some additional directions. Greater detail can be provided by using azimuths. This is a location system that uses the degrees around the circular compass starting at north and going in a clockwise direction. North is 0°. East is 90°. South is 180°, and west is 270°.
One degree to the west of north would be 359°.
Continue with the lesson