Back to basics: Navigation

“The  sun  never  sets  on  the  British  Empire”

To a degree, the story of navigation is the story of the British Empire. Don’t believe me? Well, read on! Today, maps from around the world use a system of longitudes and latitudes. These are imaginary lines all over the earth, with longitudes running from the north pole to the south pole, and latitudes encircling earth, parallel to the equator.

Before the mid-1800s, anyone was free to make their own maps, using whatever measurements they liked. While the north and south poles are fixed references, the earth doesn’t have a “west pole” or “east pole”. North and south are absolute directions, while east and west are relative to where you are. After all, if you travelled either due east, or due west, in a perfectly straight line parallel to the equator, you will eventually end up back where you are right now.

Prime  meridian

Latitudes refer to how far north, or south you are from the equator, and those values remain constant, but to determine where the centre of the map is (and therefore deciding which is east and which is west) is an arbitrary decision. That centre line is called the prime meridian, and less than 200 years ago there were multiple prime meridians in use. That meant that geographic references were dependent on whose map you were using. Britain, the birthplace of the Industrial Revolution, and centre of the British Empire, dominated the seas during that time, and the Royal Geography Society set about trying to standardise the maps.

Greenwich  Meridian

In London, you will find the Greenwich Royal Observatory, and it was here that Britain first established it’s own prime meridian, the Greenwich Meridian. It was placed where it is purely because King Charles had the Royal Observatory built in Greenwich Park, which meant, as it was a royal park, he already owned the land, and no money needed spending to first buy land. Obviously, the scientists working there were free to choose the location of their prime meridian, so they chose it to run straight through their observatory.

This was quite common, and France had its own prime meridian, running through its own observatory in Paris, while many other countries had their own prime meridian, typically running through their capital cities.

British  maps

Why does everyone use the Greenwich Meridian today? Purely because of Britain’s Empire, and navy. British maps rapidly became the de facto standard, even outside of the Royal Navy, and by the late 1800s, it’s estimated that over two thirds of all shipping used maps based on the Greenwich Meridian. This lead to President Arthur, of the USA, holding a summit in 1884, attended by 25 nations, to cement international agreement for the Greenwich Meridian to be formally recognised as what everyone will use.

Aside from national pride being a thing (and that caused France to refuse to use the Greenwich Meridian for several decades yet, before even they finally relented) it really does make sense for the entire planet to agree on which prime meridian to use. It really could have been anywhere, but in the end, we all agreed on the Greenwich Meridian.


As I said above, latitude refers to how far away from the equator you are, and it can be a positive number (north of the equator) or a negative number (south of it). There are some important latitudes that you may use in normal conversation – the tropics, and the arctic or antarctic circles. The Tropic of Cancer, in the northern hemisphere, and the Tropic of Capricorn, in the southern hemisphere are each just over 23 degrees away from the equator, and the part of the world between those two is called the tropics, or tropical area.


Longitude is the measure of how many degrees you are east, or west, of the Greenwich Meridian, and when combined with the latitude, pinpoints your position on a map just like a reference in a game of Battleships would.


In the UK, the de facto king of paper maps is Ordnance Survey, or OS Maps. Their Landranger series of maps are legendary, and highly detailed. OS Maps were formed when the British armed forces ran into trouble in Scotland, during the Jacobite uprising, and found they had no accurate maps. The Crown dictated that this must be rectified, and Ordnance Survey was founded. In a later post, we’ll examine the grid reference system commonly used by OS maps (and often commonly used elsewhere) and see how that differs from using longitude and latitude for determining where you are on the map.

Digital  maps

The world has moved on a great deal since then. Accurate maps were once seen as military assets, and therefore restricted. As recently as 15 years ago, Turkey didn’t allow civilians access to the equivalent of Landranger maps for Turkey, but then technologies such as Google Maps, and the superb Open Street Map came along and opened Pandora’s Box.

GPS (simply Global Positioning System) and later variants, such as GLONASS (built by the USSR) and Galileo (the EU’s offering) were all initially military technology, which has expanded into civilian use. In terms of navigation, our options are more wider, far more accurate, and far easier to use than the Vikings’ solar compass and sunstone, or even a comparatively modern sextant. You probably own a smartphone with integrated satellite navigation, capable of using at least the GPS, Galileo or GLONASS systems.

As in every other walk of life, you will run into purists, who proclaim that paper maps are the best. In some situations, that may well be true, but overall, digital navigation is quicker, easier and more accurate.

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