What is a Bearing?
A bearing is an angle, measured clockwise from north direction. True bearings are used in navigation to indicate the direction of one point relative to another. They are also known as ‘azimuths’ or ‘forward azimuths’ and can be expressed either as degrees (0° – 360°) or mils (0-6400). The calculation of true bearings involves using trigonometric functions and basic geometry principles. In this article, we will explain how you can calculate them yourself with some simple steps.
Step 1: Calculate the Angle Between Two Points
The first step to calculating true bearings is finding the angle between two points on a map. To do that, you need to know both latitude and longitude coordinates for each point. You can then use trigonometry equations such as the law of cosines or Haversine formula to find the angular distance between them in radians or degrees.
Law of Cosines:
This equation uses three sides of a triangle (two line segments plus their included angle) to calculate the angular distance between two points:
$$c^2 = a^2 + b^2 – 2abcos theta$$
Where c=length of opposite side; a=length adjoined side 1; b=length adjoined side 2; θ=angle between sides 1 & 2
Haversine Formula:
This equation calculates great circle distances by accounting for curvature on the surface of Earth:
$$d = 2rarcsin{sqrt{frac{(sin{frac{Δφ}{2}})^{2} + cos φ_{1}cos φ_{1}(sin{frac{Δλ}{2}} )^{²}}}$$
Where r=radius Earth ; Δφ = difference latitudes ; Δλ = difference longitudes ; φ₁&₂ = latitudes
Once you have calculated your angles, convert it into degrees if needed – remember that there are 360° in one full rotation!
