Inventor of the modern navigational chart
Gerardus Mercator was a Flemish cartographer and craftsman of mathematical instruments.
After producing traditional, but highly detailed, maps for some years, he undertook to design a map of the entire known Earth in a manner that would be useful to mariners.
The usual portolan charts were good for short voyages, but highly inaccurate for ships sailing across oceans.
Mercator’s 1569 planisphere, titled “Nova et Aucta Orbis Terrae Descriptio ad Usum Navigatium Emendate” (New and augmented description of Earth corrected for the use of navigation) was, as the name implies, specifically designed for marine navigation.
It was printed on 18 separate sheets in book form.
It was unique at its time because all lines of latitude and longitude were respectively parallel lines intersecting at right angles.
Lines of constant bearing (rhumb lines) could be depicted as straight lines, which was an impossibility with any other chart of its day.
As a result, a mariner could plot a course from a port in Europe to a location in the New World with relative ease, assuming the chart was reasonably accurate.
The major shortfall of the Mercator projection is that it is relatively useless in the polar regions since the linear scale becomes infinitely high at the north and south poles.
Several developments over the years have vastly improved the usefulness of the Mercator projection chart.
Exploration and settlement have heightened the accuracy of charts.
The development of accurate timepieces has made determination of longitude vastly easier than before.
Until the 20th century, ships relied on magnetic compasses as their principal means of determining direction at sea.
Yet it was not until the 18th century that magnetic declination was clearly understood and charted.
In the interim, blind use of rhumb line courses could lead a ship astray on a long voyage.
Even then, though, the Mercator projection chart was still vastly superior to the portolan chart.
It revolutionized marine navigation and has stood the test of time.