A compass is a navigational tool used for determining the directions relating to the Earth’s magnetic poles. The navigation compass consists of a magnetized pointer (generally marked on the north end) free to align itself with Earth's magnetic field. The navigation compass considerably enhances the safety and efficiency of travel, (specifically ocean travel). A navigation compass can be used to determine heading, used with a sextant, and marine chronometer to determine latitudes and longitudes respectively.
The navigation compass has significantly enhanced navigation capability as it has been recently replaced by modern devices such as Global Positioning System (GPS). A navigation compass is any magnetic device capable of representing the directions of the magnetic north of our planet's magnetosphere.
The face of the compass usually focuses on the cardinal points of north, south, east, and west. Usually, compasses are formed as an independent sealed instrument with a magnetized needle or bar rotating freely upon a pivot, or moving in a fluid, then able to point in a north and south direction. Keep reading to know about compass bearing.
The compass bearing is a direction towards which we are headed, as represented by the compass. The four cardinal points on a compass divide the circumference of the compass into four equal parts are north, south, east, and west. As there are 360° in circumference, the cardinal points are expressed as 360°/ 4 or 90°.
A compass rose given below represents both angle and cardinal points. The convention used for measuring angles is different from the convention we use in unit circles definition for defining trigonometric functions. The 0 degrees in the compass bearing is marked as North rather than x-axis. Secondly, the direction in which the angle increases is clockwise rather than anticlockwise.
Between the cardinal points, the other points that can be seen on compass bearing are:
North - East
South - East
The above points divide each 90-degree angle into eight. Hence, the angle between two consecutive points is given as 90°/8 or 111⁄4°.
The two compass bearing types are discussed below:
The standard cardinal directions are North, South, East, and West as shown in the figure given below:
Standard compass bearings are split into 16 different directions around a compass, each located 22.5° apart from the other. If we start from North Position and move 22.5 clockwise, we reach the NNE ( North - North East) directions. Moving another 22.5°, we reach North-East directions. This continues all the way around the clock, until we move back to the starting point.
At 45° between two pure directions, the name of the direction always initiates with North or South, that is North-East or South-West. Directions nearest to a pure direction are named on the basis of which pure direction they are nearest to, followed by North or South, or followed by the direction that is named at first. For example, ENE ( East - North East) or SSW ( South-South - West) directions.
The diagram below represents the angles and names of each of the sixteen standard compass bearings:
If you are looking for more specific headings, then you can move to the Other Compass Bearing method. This angle represents the specific angles in between two of the four more headings such as 22° West. Let us discuss how to find these directions.
Initiates with North or South
Rotates as the angle required
Find that number between North or South direction or other direction required.
The angle given in the above diagram is 30°. As the general rule is to start with the North or South direction, let’s start with the North direction and find the angle that we need to rotate through to get the read compass bearing. We can see that there are 90° between each successive pure direction. Hence, we will subtract the given angle from 90°.
Therefore, we get 90° - 60° = 30°.
Imagine, you are stuck somewhere in the middle of the road, and there are no symbols or landmarks to help you to find your way? Do you know how to find your way home? Someone may tell you through the phone to move to your left, or turn through 60°, then start moving, but how will they know which way you are pointing in the first place.
The precise method that can be used to describe directions from a point is three-figure bearings.
A compass always points in the North direction. Bearings are always measured in Clockwise directions from the North Line.
So, when someone asks you to walk on a bearing of 120°, you should face yourself towards North, turn clockwise through 120° and start walking.
The angles in three-figure bearings in degrees are measured clockwise from the North direction. It is usual to place 0° to form a 3 digit degrees as shown in the figure given below:
In the above figure,
North is shown as 000°
East is shown as 090°
South is shown as 180°
West is shown as 270°
An airplane takes off from London Airport as represented in the figure given below:
In the above figure, the angle between the north line and the flight path of the airplane is shown as 30°. Hence, we can say that airplane is flying on a bearing of 30° from.
1. What are the Limitations of the Compass?
Ans: A compass is close to the regions near the equator, which is far from the magnetic north. A compass becomes more sensitive to crossing its lines, if it moves closer to one of the magnetic poles of the Earth. The compass will not represent any direction, but will begin to drift at some point closer to the magnetic compass. Also, due to the magnetic inclination, the needle starts to point up or down as getting closer to the poles. A cheap compass with inadequate bearings may get stuck because of magnetic inclination and therefore represent inaccurate directions.
2. Which is the Earliest and Most Renowned Type of Compass?
Ans: Magnetic compass is the most earliest and renowned type of compass. It is an instrument used for determining the directions of the earth with the help of a magnetic pointer that aligns itself with the Earth's magnetic field. The magnetic compass is used in different forms in aircraft, ships, land vehicles, etc.
3. Where was the First Compass Invented?
Ans: The first compass was discovered in China at the time of the Han dynasty between the 1st century B.C. and 13 century A.D. At first, the compass was used for geomancy, divination, and fortune telling for finding precious gems. But later, people discovered that it can be used for navigation and orientation.
4. What were the earliest compasses made out of?
Ans: Earliest compasses were made of lodestone, a specific form of the mineral magnetite. Other compasses were also made of lodestone but were shaped like a spoon or ladle whose handles were made to pinpoint the south direction. In the 11th century, the China military used compasses for navigation orienteering whereas, in the 12th century, it was used for naval orienteering.
Compasses were then made of magnetized iron rather than lodestone and were known as 'south-pointing fish' which was a magnetized iron fish that floated in a bowl of water and pointed south direction.