Definition:

A conformal cylindrical map projection first presented by Flemish geographer and mapmaker Gerardus Mercator in 1569.  The meridians are equally spaced vertical lines, and the parallels of latitude are horizontal straight lines spread farther and farther apart as their distance from the Equator increases.  [REF]

Description:

While the listed name may be foreign, and the mathematic descriptors above seem complicated, essentially every elementary school student has seen one of these maps.  [REF] 

Time to dive into how this piece of cartography was created, why it rose to prominence, and what the faults of this chart system are.  To truly understand how this unique geographic documentation came into being, it’s valuable to look at the individual whose moniker the map projection bears.

Geert Kremer was born on March 5th, 1512, in Rupelmonde, Flanders, just outside of Antwerp, in the country of The Netherlands.  He was the 7th child to a poor artisan father, who died when Geert was 15 years old, at which point the adolescent went to live with his uncle, a prominent priest.

As a teenager, young Kremer attended a prestigious high school, admission aided by his relative’s connections.  Here, in addition to the religious principles of the Bible, he learned philosophy, history, and geography, which would form the foundation of a future polymath lifestyle. 

Latin was also a key part of the curriculum, which prompted the curious lad to change his name from Geert Kremer to Gerardus Mercator.  The selected last name is a Latin translation of his given Kremer title, meaning “merchant” in both cases.  Given names relating to chosen fields of occupation were common at this time throughout Europe.

Newly minted Gerardus attended the famous University of Leuven, starting in 1530; his new moniker can be found on the official historical student ledger.  Here, he diligently studied both the ancient trivium of philosophy, theology, and Greek, along with the modern quadrivium encompassing arithmetic, geometry, astrology, music.

After earning his initial “magister” degree in good standing, selecting a major field for further focus proved difficult.  There were just too many scholarly topics of interest to explore.

Possessing an inquisitive, rational, and most importantly, malleable mind, young Mercator was conflicted.  He couldn’t square the described literary creationism world presented by the Good Book, with his observations of geography and astronomy in the natural world.  This conundrum would continue to haunt Gerardus throughout his life, theology and geology in constant conflict.

Finding structure through the physical trades, in 1536 he collaborated on his first globe project, aided by a pair of more experienced practitioners.  The craftmanship displayed on this fancy orb, made from copper as opposed to wood, and leveraging Mercator’s precise italic script penmanship, cemented his place as an up-and-coming player in modern cartography.

This florid, detailed, writing style was a significant departure from the blocky, capital letters typically used in practical writing.  Displayed on the intricate artifact below, precise calligraphy became his calling card in the field of science from that point on.  [REF]

The success of this unique offering amongst the wealthy in society, and the subsequent financial gains, spurred on a wave of diligent work by Mr. Mercator.  Over the next 5 years, he refined his own skills at map research, information collation, and technical drafting.  This approach would allow him to create many new, more accurate, charts, in an era of scientific advancement where the shape of the world was literally changing by the day.

Contrary to the risky oceanic venturing by bold nautical explorers of the era, like Columbus, Drake, and Magellan, Mercator leveraged the intrepid learnings of others from the comforts of his home in Duisburg, Germany.  He poured through historical landscape reference documents housed in local libraries, and communicated via letter with travelers far afield, to map the world remotely, as opposed to making actual journeys on his own.

By middle age, acknowledge as an elite cartographer, Mercator’s offerings were highly anticipated and sought after.  He published a wall map of Europe in 1554, shown below, then Britian in detail in 1564.  [REF]

These works were both the most comprehensive and accurate geographic documentations at the time, selling very well to both technical practitioners and common citizens.  Each piece took many years to research and execute, but continued to help Mercator earn a comfortable living. 

Mercator was clearly a polymath, like many successful scientific innovators of this period.  He diligently studied numerous fields, including calligraphy, cartography, chronology, engraving, geography, geomagnetism, history, mathematics, philosophy, religion, and theology.

Most of his income came from selling tabletop globes, in both terrestrial and celestial form.  To meet the high demand, he facilitated an extensive operation encompassing manufacturing, assembly, and distribution of these units throughout Europe over the course of half a century.  As a result, many examples of this fine craftsmanship are still in existence today.

Mercator coined the term Atlas, in reference to thick books of regional maps which he bound together and sold later in life, at the end of the 16th century.  He selected the term as an ode to Greek god Atlas, the mythical king of Mauretania, who he regarded as the first great geographer, at least within the fictional realm.  By this point, the elder was acting as a knowledgeable cartography resource, with younger family members doing the precision engraving, which required deft finger dexterity.

Mercator was just as interested in the expansive heavens as he was to the home planet civilization inhabited.  During a lengthy career, he refined many scientific instruments, most notably astrolabes, which were used to define the geometry of space.

He was also quite religious as a devout Christian.  Born during the rise of the Protestantism movement, Mercator was sympathetic to Lutheran teachings, which landed him a 6-month prison sentence, decreed by Catholic overlords, during the prime of his life.  He escaped this persecution relatively unscathed, and went on to write many treatises dissecting the gospels of the Old Testament.

Mercator remarried to a wealthy widow in 1589, at the age of 77, after having 6 children with his first wife, who had passed away 3 years earlier.  He died just a short time later, in 1594, after a series of strokes, at 82 years old, which was exceedingly advanced for this era of poor sanitation and limited medication.

After death, his surviving family quickly fell into hard times, unable to capitalize on or update the Atlas map canon.  His children sold off all the books from an extensive home library amassed and used for research in 1604, for a menial sum.  While essentially all of these rare tomes have disappeared, a surviving inventory list demonstrates the breadth of Mercator’s intellectual exploration, from history to theology, mathematics to medicine.

Other savvy cartographers bought the rights to all his original copper plates, continuing to update and print both individual country maps, along with the famous global Mercator projection, up through 1599, before more geographically accurate maps were developed.

How was the Mercator projection derived?  What made this map so groundbreaking?  Why are there obvious distortions in the continental shapes?  To answer these questions, a deep dive into the means of creation for this clever piece of cartography is necessary.  Time for some math fun. 

The origins of this unique type of projection are heavily debated.  Some Chinese Song dynasty star charts exhibited similar rectangular cartography.  13th century documentation of port cities around the Mediterranean Sea displayed a linear linkage format.  German engraved maps dating back to 1511 used sundials to produce cylindrical projections across a wide range of global latitudes.

Yet, the most popular version using this hybrid cylindrical projection approach bears the name of one man.  Gerardus Mercator.

Ironically, while typically very diligently in documenting his work, through scientific papers and daily journals, there’s no record of the actual mathematical approach used by Mercator for his novel projection.  Fortunately, historical scholars have been able to piece together his probable derivation approach, as simplified in the following schematic.  [REF]

The actual calculations were much more complicated, and very sophisticated for the time.  Thus, it’s widely accepted that this innovation was substantially aided by loxodromic tables created by his close friend, Portuguese mathematician and cosmographer Pedro Nunes.

Loxodromic is not a common word in the English lexicon.  Unfortunately, neither are rhumb lines, the synonym for this rare term.

Definitionally, a loxodrome or rhumb is an arc drawn on a globe which intersects all lines of latitude at the same angle, resulting in a constant azimuth trajectory.  This concept is much easier grasped in picture format, as displayed in the subsequent diagram.  [REF]

The Age of Discovery around the globe, with nearly all this exploration being conducted via the expansive oceans, meant that more accurate maps were needed.  Mariners quickly found plotting a constant heading at sea resulted in drastic deviations from their plotted chart course on long voyages.  It turned out the earth wasn’t flat after all.  

Understanding this challenge, through scientific reasoning and analytical calculations, as opposed to traditional naval captain experience, Gerardus Mercator was the first individual to include these rhumb lines on a physical globe in 1541.  Eventually realizing their relevance for oceanic transport, nearly 2 decades later, in 1569, he finally created a flat projection of these novel globes.

Flat and rectangular in shape, while preserving cylindrical orb intersection angles across the map; this scheme allows straight line bearings to be plotted with ease.  These specific characteristics make Mercator’s derivation perfect for achieving constant true navigational headings over long oceanic distances, which was this chart’s original intent.

The original map was massive, 2 meters by 1.2 meters, encompassing 18 separate sheets of paper.  When translated from Latin, the period’s language of science, Mercator’s masterpiece was titled "A new and augmented description of Earth corrected for the use of sailors".  Despite this florid verbiage, it was clear that Mercator had a strong understanding of global navigation, and the beneficial role his map could play in this burgeoning field.

Over first half of the 1600’s, well after Mercator’s death, this unique approach to cartography was formulaically refined, primarily by a trio of independent English mathematicians.  This system was a major revolution on nautical cartography, however adoption by sailors was slow, for a pair of key reasons.  There wasn’t a reliable tool for determining latitude while at sea, and magnetic as opposed to geographic directions were the primary means of vessel guidance.

It took another 2 centuries, and a duo of additional naval navigation discoveries, for Mercator’s most unique and original map to become fully relevant and appreciated.  Namely, invention of the marine chronometer leveraging celestial bodies for accurate positioning, along with precisely quantifying the declination between magnetic and true north using onboard instrumentation.

Long overdue, the Mercator projection became the most popular global exploration map during the 18th century, the representation of rhumb lines as straight lines finally possible to be followed and exploited.  Especially by steam powered vessels, which were no longer constrained by the prevailing winds for speed and direction.

By the start of the 1900’s, the Mercator projection had been adopted and proliferated as the most useful map of the entire world.  As such, it soon took over as the dominant format for both educational and commercial applications.

Like every new publishing innovation, there were many critics.  The most frequent complaints came with regard to the size distortion of landmasses around the poles of the globe.  Here's a few basic examples which demonstrate the geographical shortcomings of Mercator’s misleading map, which can be cross references in the overlay.  [REF]

While the northernly Greenland appears larger than the entire continent of South America, in reality its landmass is smaller than the Arabian Peninsula.  Ellesmere Island, located in the Canadian arctic, projects essentially equal in size to the entirety of equator-adjacent Australia, hiding a 20X disparity in actual size. 

On the city level, north versus south issues also compound.  Oslo, the chilly capital of Norway, models as 75% larger than the steamy sanctuary of Singapore, a much bigger and more developed metropolis in this modern era. 

The cylindrical conformational projection format severely alters the size and shape of bodies at extreme northern and southern latitudes.  Some level of distortion is inherent to any map projection, a result of converting a 3-D sphere to a 2-D sheet.  The key is to force the manipulations to the least critical portions of the globe.

Which Mercator did; the poles of Planet Earth were essentially unexplored and forgotten in the 16th century.  However, these days, cargo ships brave the icy waters, and transcontinental planes arc over Antarctica.  While the Mercator projection map is now out of vogue for navigation, but still remains relevant in other elements of daily life.  Namely, online content.  

Despite its faults, Mercator’s creation is still commonly used on the internet, due to its cleanly flattened form, resulting in a defined grid structure.  The full chart becomes a near-perfect square when truncated at the 85° latitudes.  This format, known as the Web Mercator in programming terms, pervades the web, including as the basis for the ubiquitous Google Maps starting in 2005, before being updated and phased out in 2017. 

The Mercator grid layout allows for easy scaling adjustment from the entire world to tiny outcroppings, without any shape changes.  This digital format is very simple for toggling, scrolling, and zooming, making it the preferred online medium for most mapping apps.

Granted, comparing landmass size across different global parallels isn’t possible with this system.  Don’t use the Mercator projection for any application which requires comparison of widely separated terrestrial elements.  In addition, it’s not possible to create thematic maps that overlay location-specific additional content, due to the areal distortions of the Mercator format.

Even if the Mercator projection global map isn’t the most accurate, now that we know much more about the shape and scale of the planet humans inhabit, it’s still worth hailing as a compelling cartography innovation.  Not just for the novel geography learnings, but also for the impressive calligraphy with which this content was display.  Science and art, deftly intertwined.  [REF]