FlaT eaRth ( on Maps onlY , mInd !)
FulL ciRcle
FlyIng HiGh
FlaT eaRth ( on Maps onlY , mInd !)
The standard navigation map is a Mercator projection . It ’ s a way of representing the three-dimensional Earth on a two-dimensional map . Everything is in the right place in relation to each other , but there is a compromise .
Can you see how the vertical lines of longitude are equally spaced ? On a globe they would get narrower as you approach the poles , eventually meeting at a single point . Keeping them equally spaced creates a distortion , with land near the poles being stretched wider than it is in reality .
Notice how the horizontal lines of latitude are not evenly spaced ? They get further apart towards the poles , making
the land in those areas appear much longer than it really is . More distortion !
In the Mercator projection , Africa might look the same size as Greenland , but it ’ s actually 14 times larger !
FulL ciRcle
The shortest route on a Mercator projection is a straight line that crosses the vertical longitude lines at the same angle every time . This is called a rhumb line ( RL ). But it won ’ t actually BE the shortest route , especially in the most distorted parts of the map !
Rhumb Lines
Since we ’ ll be travelling in 3D space , we need to go back to a 3D globe to find the shortest route .
When you plot a straight line between two places on a globe , it will always be part of a great circle – an imaginary slice through Earth , which cuts it into two equal halves . A rhumb line can only be a great circle if it follows the equator or travels directly north-south . Otherwise , if it carried on , it would spiral in towards the nearest pole .
Possible Routes
The black line on this Mercator projection shows the approximate route the Titanic took from Cork , in 1912 . The red line shows the great circle route , the shortest possible journey – though obviously Titanic wouldn ’ t have gone over land . The great circle route is about three per cent shorter than the rhumb line ( green ). It would have saved time and fuel – but passed through icy waters .
Titanic sailed a longer , more southerly route . Whatever the reasons why , we can safely say it was not a Blue Riband attempt !
FlyIng HiGh
Great circle routes work better for aircraft than for ships . This is why if you were to travel from Paris to Vancouver , you would fly over the UK and Greenland , as opposed to spending a lot of your journey over the Atlantic Ocean !
Flightpaths are also subject to air currents and conflicts . International flights are currently avoiding Russia and Ukraine , causing a surprising number to take a great circle polar route . Check this for yourself at www . flightradar24 . com . Just click on a plane to see its route .
Try making your own great circle routes between airports using this interactive map :
Mercator projection map www . greatcirclemapper . net
AWESOME
ACTIVITIES ALERT
SCAN ME
Follow this link to make your own globe and explore more !
Words : Sarah Bearchell . Illustration : Jack Tite
17