Mon | Feb 19, 2018

A Matter of Land | Wise men and land surveyors follow the star

Published:Sunday | December 31, 2017 | 12:00 AMCraig Francis
Craig Francis
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The Bible, as part of the Nativity, tells of three wise men using the stars as a means of navigation to guide them to finding the Baby Christ after His birth.

Just like the wise men, who used the stars to guide them, surveyors, before the advent of global positioning systems (GPS), and other established methods of orientation and navigation, used the celestial bodies to determine position and orientation.

By measuring angles to certain stars, the land surveyor is able to determine his position and orientation for any given place or line. This method of arriving at position and orientation is still taught at the University of Technology to all the student land surveyors.

 

EASY TO NAVIGATE WITH STARS

 

Lots of people love the idea of finding direction and navigating using the stars, but are put off because they think it is complicated. It does not need to be complicated at all. You just need to know what to do. In fact, finding direction using the stars is fun.

Fortunately, there is one star in the night sky that does not appear to move. It is called Polaris, or the North Star.

The easiest method for finding the North Star is by finding the 'Plough', an easy-to-identify group of seven stars also known as the Big Dipper.

Next, you find the 'pointer' stars. These are the two stars that a liquid would run off if you tipped up your 'saucepan'.

The North Star will always be five times the distance between these two pointers in the direction that they point (up away from the pan). Polaris is the brightest star in the 'Little Dipper' constellation. True north lies directly under this star.

The 'Big Dipper' rotates anticlockwise around the North Star, so it will sometimes appear on its side or even upside down. However, its relationship with the North Star never changes and it will always dependably point the way to it.

The reason the North Star is so important for natural navigation is that it sits directly over the North Pole. Something that people often forget is that whenever you are trying to find true north, you are actually trying to find the direction of the North Pole from wherever you are. Even if you are only heading a few hundred metres on a gentle walk, north is still just an abbreviation for towards the North Pole.

The constellation Cassiopeia is also very helpful in finding the North Star as it will always be on the opposite side of the North Star from the Big Dipper and, therefore, often high in the sky, when the Big Dipper is low or obscured.

Having found the North Star, there is something about its height above the horizon that is well worth knowing. Wherever you are in the northern hemisphere, the North Star will be the same angle above the horizon as your latitude.

This can be measured accurately using a sextant, but an estimate can be made using an outstretched fist. We are all different shapes and sizes, but we share proportions. An outstretched fist makes an angle of close to 10 degrees for most people.

In an under a minute, and with just your bare hands, you can now find north and estimate your latitude.

The constellation, Orion, rises in the east and sets in the west. Orion's belt - the only three bright stars that form a short straight line in the whole night sky - rises very close to due east and set very close to due west.

If you want to be really accurate, then the first star in the belt to rise and set, called Mintaka, will always rise and set within one degree of true east and west wherever you are in the world.

So tonight, go out and look up at the stars and try to determine your latitude. It should be fun, and like the wise men, follow the star.

Keep sending your questions and comments and let's continue to explore A Matter of Land. Until next time, traverse well.

- Craig Francis is a commissioned land surveyor and managing director of Precision Surveying Services Ltd. He can be contacted for questions or queries at craig_r_francis@yahoo.com or Precision Surveying Services.