Find latitude using pole star without a GPS



A pole star is a star that is aligned to the axis of rotation of Earth. We have a current northern pole star called Polaris (Alpha Ursae Minoris), which is closely aligned to the north pole. And we also have a current southern pole star called Sigma Octantis (Polaris Australis). These stars are helpful in the celestial-based navigation.

Find latitude in the northern hemisphere.
If you are located in the northern hemisphere, the latitude of your exact position can be determined using the pole star Polaris. Polaris is a bright star with a magnitude of 2 and can be easily seen with your naked eye.

  • To determine your latitude, you will have to measure the angle between Polaris and your horizon.
  • For example, if you are located exactly at the north pole, then Polaris will be right above your head. So, it’s angle will be 90°. Latitude will be 90° too.
  • Similarly, if you are located at the equator, Polaris will be at your horizon, which is a 0° angle, i.e., the equator.
  • Measuring that angle between Polaris and the horizon from your position will give you the angle of latitude.

Find latitude in the southern hemisphere.
If you are located below the equator, i.e., in the southern hemisphere, then Sigma Octantis is your pole star. It is a fainter star with a magnitude of around 5.47 which varies about 0.03 every 2 hours and 33 minutes. Just follow the same procedure as stated above but with Sigma Octantis as your reference star.

Note: This method of calculation will not provide the accurate angle of latitude.

Find longitude using the time.
You can calculate the longitude using the time difference between the local mean time and the Greenwich mean time. To find longitude, read this tip.

Find longitude using time without a GPS