Cardinal points, traditionally represented in the compass rose, are 4 orthogonal points that are used to orient anywhere on Earth.
The compass rose is also called a “wind rose” because each quadrant represents a wind (for a total of 4 quadrants).
First concept to be debunked: the idea of “North” is quite broad.
We actually have different types of North.
True North represents the North Pole, the end of the Earth’s axis.
By Magnetic North, on the other hand, we mean the magnetic field that draws the compass to itself.
However, this is affected by deflection (the effect that the electrical and metal equipment of the vessel has on the compass).
This results in the North of the Compass.
North on the map
Looking at a map and even a compass rose, North is at the top, South at the bottom, East at the right, and West (denoted by the letter W of West) at the left.
This is a convention.
Compass
The compass that is used in navigation is the liquid magnetic type. Its parts are:
1) Mortar or case: non-magnetic casing, often supported by a binnacle;
2) Binnacle: column made of wood, resin, or nonmagnetic metal;
3) Gimbal suspension: keeps the compass parallel to the horizontal plane;
4) Liquid: white oil, glycerin or mixture of water and pure alcohol. These substances absorb shocks and thus provide some stability to the compass. Also, they don’t freeze at low temperatures;
5) Compass rose: graduated disk containing the 4 cardinal points, as we saw just above. It is oriented toward the north;
6) Pointer: is a pivot that starts from the mortar and supports the float;
7) Float: it is immersed in the liquid and reduces the pressure and friction on the suspension tip;
8) Magnetic needles: the needles keep the compass rose oriented in the north direction;
9) Line: it can be a line, or a pivot. The role of the line is to indicate to the boat’s bearer the direction of the heading. If the compass on board is oriented correctly, the line is oriented as the longitudinal axis of the boat;
10) Lung: is a bag that depending on the expansion or restriction due to temperature adapts to the liquid by decreasing or increasing in volume;
11) Cover glass;
12) Compensators: are mounted on skids and moved closer or further away from the compass. They serve to reduce edge deviations (those we discussed above in relation to the north of the compass).
How to read a compass
1) Horizontal reading
In horizontal reading, the observer should imagine that he or she is in the center of the compass and compass rose, as is true for compasses on nautical charts. The line is at the top of the compass.
2) Frontal reading
In frontal reading the iv compass rose is only represented for one part, so as not to confuse the observer. It is not instinctive at all because it involves the observer imagining himself externally, facing the line and thus looking South.
Normally, the cover of this compass is domed.
Tips for using the compass
- The compass rose is integral to the needles. Both will therefore point to the north;
- To avoid deviation, it is best to keep metal objects or objects that produce magnetic fields away from the compass. So it is best to keep cell phones, keys, GPS away from it.