What is Compass ?
A compass is an orientation instrument, which allows the traveler to locate himself spatially with respect to magnetic north by means of a magnetized needle. It is a fundamental instrument for sailors, hikers, pilots, hunters, explorers, etc.
The first compass emerged in China. It was used primarily as a navigational instrument that allowed overseas travelers to orient themselves in space and define the path to follow, but it was not infallible. Over time, other compass systems were developed.
Parts of a compass
There are several types of compasses. All of them basically share three fundamental elements: a base with a ruler and a reference arrow; a limbus or graduated disk that rotates on its own axis and a magnetized needle that points north.
Today there are many varieties of compasses available, as the systems have been perfected with the advancement of technology.
The magnetic compass, the oldest of all, allows orientation through the magnetic needle system that points towards the magnetic north pole of the earth, that is, from the identification of the earth’s magnetic field.
The gyroscopic compass or gyrocompass always looks to the geographical north and not to the magnetic one, as it uses a set of rings and a disk aligned according to an axis of rotation, the inner and outer axes, which are perpendicular to each other.
Other types of compasses can be the limbo compass, lentic compass, cartographic compass, electronic compass and mobile phone compass. The latter depends on the availability of the network at the site of the scan, so it can be insecure.
To indicate the direction we use expressions such as “to the right”, “to the left”, “straight ahead”, and so on. But then the question arises: “To the right … of what? The reader of a map needs to know the exact address and have a method that can be used anywhere in the world, with a common unit of measurement. Maps they formulate the address in angular units, using various systems.
The basic directions are North, East, South and West, at 90º intervals following clockwise. These are the universally accepted cardinal points. Between them, at 45º are its sides, which are indicated by joining the initials of the cardinal points that are on both sides, starting with N or S. In this way you will obtain the NE, SE, SW and NW. Less used are the intermediate points between the eight laterals, called collaterals, which are indicated by gathering the initials of the points that are on each side, starting with the single letter, that is, NNE, ENE, ESE, SSE, SSO (ssw ), OSO (wsw), ONO (wno) and NNO (nnw).
It is possible to improvise a compass to see how our ancestors discovered its properties. Iron and steel can become magnetized. No other metal has this property. If you rub a steel needle with a magnet, it will acquire part of the magnetism of the magnet. It can also be magnetized with an electric coil through which an electric current is circulated.
To make a simple construction, cut a disc from a cork stopper and place a magnet needle on it in a container of water. You will see that it rotates to go North-South once it stops oscillating.
Another way to hold the needle is to tie a long thread at its equilibrium point. If you hold the other end of the thread and let the needle hang, it will end up stopping in the North-South direction. This version is more portable than the floating needle, and can be used for orientation.
The hand compass is the most commonly used and simplest instrument for determining directions and measuring angles. It comes in various styles, from the simple pocket or wrist compass to more complicated models such as the Slyva, the military, etc. All styles are navigational in their basic concept. The compass used to navigate is also called a compass. All compasses must have a cover that protects the sphere or lens against dust or anything that can damage them.
The Slyva model consists of a compass attached to a transparent plastic sheet with graduated edges like those of a slide rule. These edges is clearly marked with an arrow that is made to coincide with the direction taken.
Brunton type compass:
The “Brunton” compass is generally used for heading and hold measurements. In other words, ” half-circle ” and “” type measurements . Also measurements of the “full circle” concept are possible. The “Brunton” compass exists in the azimuthal version (from 0 to 360º) and in the quadrant version (each quadrant has between 0-90º).
- The compass is in heading orientation, next to the rocks
- The bubble of the spherical level must be in the center
- The needle has to be free
- Take the bearing value N ….. E or N ….. W
To take the bearing value, only quadrants I (between 0 and 90º) or quadrant IV (between 270º and 360º) are used. It means the needle that marks between 0-90º or between 270-360º is the reading needle . It can be the black marlin or the white marlin. There are two possibilities:
One of the needles marks between 0-90º azimuthal (quadrant I): N [value] E is automatically taken . In this case an “E” always appears.
One of the needles marks between 270º-360 azimuth (quadrant IV): We have to use the distance between north and the needle or as a formula: N [360º-value] W. In this case a “W” always comes out.
- The compass is placed perpendicular to the heading
- The clinometer is used
- The bubble of the tube level must be in the center
- The clinometer reading is taken as a hold
The clinometer reading is taken on the clinometer scale , below the azimuth scale. This value, not greater than 90º.