Mercator projections – changing navigation

Gerardus Mercator

Gerardus Mercator was a sixteenth century Belgian cartographer. In 1569 he created a world map based on straight lines of contstant course known as rhumb lines. He successfully presented a three dimensional object (the world) on a two dimension piece of paper. For the mathematical minded amongst you its a line that creates an arc on a constant course – I tend to think of it as cutting the world into sections straight through the middle of the planet like so many slices of cake at a constant angle (its not a right angle) but I have the feeling that I have horribly over simplified and may have become fixated on the cake part of the equation…but you get the gist.

Essentially Mercator used the rhumb lines which were constant to draw his charts and maps. He imagined the world, or a chart, as a piece of paper which was rolled into a scroll. This enabled him to link all the lines of latitude (east west lines) that we imagine going around the world. So far so good and on a small scale it works well. But a problem arises because the world is not a cylinder – it’s a sphere. This means that the lines of longitude (the north south lines) are distorted and if you draw countries based on the straightened out lines the countries at the top of the map like Antartica and Siberia look much bigger than they really are unless you draw the segments so that the top of the world looks like a series of fingers with white paper between them – which isn’t great if you’re trying to navigate somewhere. So having ruled that option out the Mercator projection makes Greenland looks huge – bigger than Africa and that folks is just not true! But Mercator was creating charts for sailors – the oceans needed to be right for them to make navigational decisions not so they could compare the relative size of land masses. Nor does it help that the world is ‘Old World’ centric – the sailors were setting off from the known world into the New World. Basically a world map based on Mercator Projections sees its priorities through sixteenth century eyes.

Essentially, anything past 70degrees latitude isn’t quite the right shape on a map created using Mercator’s projection. Corrections were made even in the sixteenth century but we’re not going there today because that’s more than enough for my brain to cope with in one go. Suffice it to say at the time it was an excellent step forward because it made navigation by mathematical means far easier.

Robert Dudley, calling himself the Duke of Northumberland and the Earl of Warwick was the first Englishman to create an atlas of the sea using mercator’s projections. It was published in 1646-1647 in Florence. It contained more than 100 beautifully engraved maps.

10 thoughts on “Mercator projections – changing navigation

  1. Well, which Robert Dudley? bc his father John was Northumberland & his brother Ambrose was Warwick. QEI’s Robert Dudley (d.1588) was Earl of Leicester Thanks!

    • None of the above! Robert Dudley (1574-1649) was the illegitimate son of Robert Dudley, Earl of Leicester. Ambrose was his godfather. he inherited the bulk of both his father and uncle’s estates but not the title. he left England following a court case to establish that his mother Douglas Sheffield was married in a clandestine ceremony to Leicester (which would have made Leicester’s subsequent marriage to the Countess of Essex bigamous). In France Dudley converted to catholicism, married his cousin Elizabeth Southwell despite the fact he was married to Alice Leigh and had four daughters at home, moved to Florence and spent the rest of his life working for the Medici. He took on the titles Duke of Northumberland and Earl of Warwick but obviously the Stuarts didn’t recognise the titles.

      • No worries and its always good to check – Robert Dudley junior is usually a footnote at best so it does initially read oddly when you think about how much we know about Robert Dudley, Earl of Leicester. Douglas and her son usually get written out of the story.

    • Its not in the same league as the Sandwich or Wellington boots – I wonder if its because the name sounds as though its got something to do with merchants…

    • Lady Douglas or Douglass Sheffield was born Douglas (s) Howard. Her godmother was Margaret Douglas, Countess of Lennox – Henry VIII’s cousin. Traditionally girls were named after the most important of their two godmothers or that godmother had the choice in their naming. Why her parents didn’t choose Margaret is slightly beyond me! Douglas’s own god daughter was also lumbered with the name Douglas.

      • True. It’s so interesting though, esp. bc he was SO desperate for an heir, to not take one he had already. I work on Penelope Rich so was just reading how she was against him when Jr. came back in the 90s looking for some inheritance.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.