Category Archives: navigation

Rising and Setting Times of Stars.

Posted on June 9, 2014 by Jack Case

It is very useful to be able to calculate the times at which the principal stars and constellations will rise in the east.  It is also helpful to be able to predict the approximate position of the star or constellation … Continue reading →

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How To Locate The Pole Star (Polaris)

Posted on August 29, 2012 by Jack Case

First step – Look in the northern sky to find the constellation Ursa Major which is otherwise known as the Great Bear. Second step – find the Big Dipper (marked in red) which consists of the seven brightest stars of the constellation … Continue reading →

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The Southern Cross

Posted on August 29, 2012 by Jack Case

Just as we can use the Pole Star in the northern hemisphere to find the direction of north, we can use the Southern Cross in the southern hemisphere to find the direction of south.   However, whereas we can use the … Continue reading →

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The Rhumb Line

Posted on August 29, 2012 by Jack Case

If a ship were to steer a steady course, that is one on which her heading remains constant, her track would cut all meridians at the same angle, as the following diagram shows.  Such a line on the Earth’s surface … Continue reading →

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The Relationship Between Longitude, Latitude and the Nautical Mile.

Posted on August 29, 2012 by Jack Case

The Relationship Between Longitude and the Nautical Mile.  The Earth’s equatorial circumference is 21640.6 n.m.  Since the Equator is a great circle, 1o will subtend an arc of:  21640.6 ÷ 360 =  60.113  ≈ 60 n.m. There are 360 meridians of Longitude so … Continue reading →

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Titanic and the Traverse Tables

Posted on January 8, 2012 by Jack Case

Recent discussions regarding the possibility that the SOS position sent by the Titanic was incorrect due to mistakes made in applying the traverse tables make interesting reading. Traverse tables have been used for about 200 years to solve the mathematical … Continue reading →

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Finding Latititude In A Survival Situation.

Posted on January 8, 2012 by Jack Case

The  full method of calculating your latitude from the altitude of the Sun can be found at this link.  However, in a survival situation, the following simplified method can be used. Equipment Needed.  A clinometer or other device for measuring angles. … Continue reading →

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Latitude from Polaris

Posted on January 8, 2012 by Jack Case

Using The Pole Star (Polaris)  To Find Your Latitude Assume that the Pole Star (Polaris)is exactly in line with the Earth’s axis produced, as shown in the following diagram. To an observer O on the Equator (lat. 0o) the Pole … Continue reading →

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