Azimuth Calculator

Created by Bogna Szyk
Reviewed by Steven Wooding
Last updated: Jul 28, 2022

This azimuth calculator will let you calculate the azimuth from the latitude and longitude of two points. It will tell you which direction you need to point your compass to and what is the shortest distance between two points of known geographical coordinates. This article includes a short explanation of the formulas we used – they can prove themselves helpful if you plan to find the azimuth by hand.

This is not a spherical coordinates calculator – it deals with geographical coordinates only!

What is the azimuth?

By the US Army definition, the term azimuth describes the angle created by two lines: one joining your current position and the North Pole, and the one joining your current position and the distant location. Azimuth is always measured clockwise!

For example, a point lying east from you would have an azimuth of 90°, but a point lying west from you – 270°.

The azimuth is used when indicating a position in the sky too: it marks the horizontal direction. The altitude indicates the vertical direction varying from 0 (the horizon) to 90° (the zenith).

The point opposite to the zenith is called the nadir. Your antipode lies at the nadir: calculate it with our antipode calculator!

Azimuth formula

If you want to give a location of a point relative to your current position, you need to provide two values: the azimuth and the distance. If Earth were flat, the latter would simply be the straight-line distance between two points. As Earth is a sphere (or, more precisely, a geoid), it is the shortest travel distance between the two points ('as-the-crow-flies').

To calculate the distance dd between two points, our azimuth calculator uses the Haversine formula:

a= sin2(Δϕ2) +cosϕ1cosϕ2sin2(Δλ2)\footnotesize \begin{align*} a =\ &\sin^2\left(\frac{\Delta\phi}{2}\right)\ +\\ &\cos \phi_1 \cos\phi_2 \sin^2\left(\frac{\Delta\lambda}{2}\right) \end{align*}
d=2R arctan2(a,1a)\footnotesize \begin{align*} d &= 2R\ \text{arctan}2(\sqrt{a}, \sqrt{1-a}) \end{align*}

where:

  • ϕ1\phi_1 – Latitude of the initial point (positive for N and negative for S);
  • ϕ2\phi_2 – Latitude of the final point (positive for N and negative for S);
  • λ1\lambda_1 – Longitude of the initial point (positive for E and negative for W);
  • λ2\lambda_2 – Longitude of the final point (positive for E and negative for W);
  • Δϕ=ϕ2ϕ1\Delta\phi = \phi_2 - \phi_1;
  • Δλ=λ2λ1\Delta\lambda = \lambda_2 - \lambda_1;
  • aa – An intermediate step; and
  • RR – Radius of the Earth, expressed in meters (R=6371 kmR = 6371\ \text{km}).

Input latitudes and longitudes in the decimal degrees notation.

You can find the azimuth θ\theta using the same latitudes and longitudes with the following equation:

θ= arctan2(sinΔλcosϕ2,cosϕ1sinϕ2sinϕ1cosϕ2cosΔλ)\footnotesize \! \begin{align*} \theta =\ &\text{arctan2}(\sin\Delta\lambda\cos\phi_2,\\ &\!\!\cos\phi_1\sin\phi_2 - \sin\phi_1\cos\phi_2\cos\Delta\lambda) \end{align*}

How to calculate the azimuth: an example

Let's assume we want to calculate the azimuth and distance required to determine the position of Rio de Janeiro respective to London. All we have to do is follow these steps:

  1. Determine the longitude and latitude of London – our initial point. We can find that ϕ1=51.50°\phi_1 = 51.50\degree (positive because it lies in the northern hemisphere) and λ1=0°\lambda_1 = 0\degree.

  2. Determine the longitude and latitude of Rio de Janeiro – our final point. We can find that ϕ2=22.97°\phi_2 = -22.97\degree (negative, because it lies in the southern hemisphere) and λ2=43.18°\lambda_2 = -43.18\degree (also negative, because it lies in the western hemisphere).

  3. Calculate the change in latitude:

Δϕ=ϕ2ϕ1=22.97°51.50°=74.47°\footnotesize \qquad \begin{align*} \Delta\phi &= \phi_2 - \phi_1\\ &= -22.97\degree - 51.50\degree\\ &= -74.47\degree \end{align*}
  1. Calculate the change in longitude:
Δλ=λ2λ1=43.18°0°=43.18°\footnotesize \qquad \begin{align*} \Delta\lambda &= \lambda_2 - \lambda_1\\ &= -43.18\degree - 0\degree\\ &= -43.18\degree \end{align*}
  1. Insert all of the data into the Haversine formula to calculate the distance:
a= sin2(Δϕ2) +cosϕ1cosϕ2sin2(Δλ2)= sin2(74.47°2)+cos(51.50°)cos(22.97°)sin2(43.18°2)=  0.443d=  2R arctan2(a,1a)=  2×6371× arctan2(0.443,10.443)=  9289 km\footnotesize \quad\enspace \begin{align*} a =\ &\sin^2\left(\frac{\Delta\phi}{2}\right)\ +\\ &\cos \phi_1 \cos\phi_2 \sin^2\left(\frac{\Delta\lambda}{2}\right)\\[1em] =\ &\sin^2\left(\frac{-74.47\degree}{2}\right) +\\[.7em] &\cos (51.50\degree)\cos(-22.97\degree)\\[.7em] &\sin^2\left(\frac{-43.18\degree}{2}\right)\\[1em] =\ &\ 0.443\\\\ d =\ &\ 2R\ \text{arctan2}(\sqrt{a}, \sqrt{1 - a})\\ =\ &\ 2\times 6371 \times\\ &\ \text{arctan2}(\sqrt{0.443}, \sqrt{1 - 0.443})\\ =\ &\ 9289\ \text{km} \end{align*}
  1. Calculate the azimuth from the azimuth equation:
θ= arctan2(sinΔλcosϕ2,cosϕ1sinϕ2 sinϕ1cosϕ2cosΔλ)= arctan2(sin(43.18°)cos(22.97°),cos(51.50°)sin(22.97°) sin(51.50°)cos(22.97°)cos(43.18°))=2.455 rad\footnotesize \quad\enspace \begin{align*} \theta =\ &\text{arctan2}(\sin\Delta\lambda\cos\phi_2,\\ &\cos\phi_1\sin\phi2\ -\\ &\sin\phi_1\cos\phi_2\cos\Delta\lambda)\\\\ =\ &\text{arctan2}(\sin(-43.18\degree)\\ &\cos(-22.97\degree),\\ &\cos(51.50\degree)\sin(-22.97\degree)\ -\\ &\sin(51.50\degree)\cos(-22.97\degree)\\ &\cos(-43.18\degree))\\\\ = & -\!2.455\ \text{rad} \end{align*}
  1. Convert the azimuth to a positive degree value:
θ=2.455 rad=140.65°=219.35°\footnotesize \quad\enspace \begin{align*} \theta &= -2.455\ \text{rad}\\ &= -140.65\degree\\ &= 219.35\degree \end{align*}
  1. Congratulations! You have just calculated azimuth from latitude and longitude.

FAQ

How do I calculate the azimuth from latitude and longitude?

You can calculate the azimuth between the points (ϕ₁, λ₁) and (ϕ₂ λ₂), where ϕ is the latitude and λ longitude, as follows:

  1. Compute x = sinΔλ × cosϕ₂, where Δλ = λ₂ - λ₁ is the difference in longitudes.
  2. Compute y = cosϕ₁ × sinϕ₂ - sinϕ₁× cosϕ₂ × cosΔλ.
  3. Finally, find atan2(x,y), i.e., the angle in the standard plane between the positive x-axis and the segment joining (0,0) and (x,y).

How do I set the azimuth of my satellite dish?

Azimuth is the angle by which you must rotate the whole antenna around a vertical axis to get the signal. Azimuth is given in degrees from North. This means North is 0 deg, East is 90 deg, South is 180 deg, and West is 270 deg. Hence, if the required azimuth is 120 deg, you must point your dish in a South-Easterly direction and slightly more to the East than to the South.

How do I determine the azimuth in astronomy?

In astronomy, the azimuth is the angle of the object measured around the horizon. We use it, along with altitude, to describe the position of an object on the celestial sphere. Usually, azimuth is measured from true North increasing eastward. Hence its value is:

  • for an object located due North of the observer;
  • 90° for an object due East;
  • 180° for an object due South; and
  • 270° for an object due West.

However, there are exceptions where we measure, e.g., from true South increasing westward!

Bogna Szyk
Starting point
Latitude
deg
Longitude
deg
Final point
Latitude
deg
Longitude
deg
Azimuth
Distance
mi
Azimuth
deg
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