Christopher Columbus:
A case study on why consistent units of measurement matter.
Landing of Columbus, by John Vanderlyn, 1847. Christopher Columbus is depicted landing in the West Indies, on an island that the natives called Guanahani and he named San Salvador, on October 12, 1492. He raises the royal banner, claiming the land for his Spanish patrons, and stands bareheaded, with his hat at his feet, in honor of the sacredness of the event. The captains of the Niña and Pinta follow, carrying the banner of Ferdinand and Isabella.
When Christopher Columbus landed on Guanahani island in the Bahamas, he truly believed that he’d reached the East Indies. Despite mounting evidence to the contrary (including Columbus’ three additional voyages), he continued to publicly claim he’d found India for the rest of his life.
As surveyors know, unit of measurement is essential in correctly calculating distances. For example, it’s only since December 31, 2022 that the precise measurement of a foot was standardized to be 0.3048 meters. Previously, two standards were used – the U.S. Survey Foot (1200/3937 meters), and the international foot, 0.3048 meters. That’s a difference of only one one-hundredth of a foot per mile[1]. Though the difference is miniscule, small differences turn into big differences over long distances.
The voyage of Columbus is a clear example of how small differences in measurement can change everything.
No Flat Earth Theory
Back in the 1400s, most people didn’t believe the earth was flat – even Medieval and Renaissance European universities taught that the Earth was round. Christian leaders and scholars all agreed on a spherical Earth[2]. The question that remained was, how big was the sphere?
Comparison of Toscanelli’s map (yellow) to the Americas (gray) (“Cippangu” was a name for Japan). A literary and historical atlas of America, by Bartholomew, J. G. Image: Public domain.
Back in 240 BCE, Eratosthenes of Cyrene calculated that the circumference of the earth was 250,000 stadia (24,854 miles/40,000 kilometers) – a remarkably accurate finding, considering that the actual equatorial circumference is (24,901 miles/40,075 kilometers).
A few years later, Posidonius, a Greek polymath, used a different method to calculate the circumference of the earth using the arc measurement method, by reference to the position of the star Canopus from Alexandia, Egypt and Rhodes, Greece. He assumed the distance from Rhodes to Alexandria to be 5,000 stadia due north. Unfortunately, he was wrong about the distance and the arc measurement, producing an erroneous estimate of 240,000 stadia (23,488 miles /37,800 kilometers); about 1,413 miles short.
1,700 years after Eratosthenes's death, Christopher Columbus studied what Eratosthenes had written about the size of the Earth, but continued to look for other sources. Subsequently, Columbus saw the calculations of the Arabic mathematician Al-Farghani who correctly calculated that the circumference of the earth was about 20,400 miles. Unfortunately, Columbus assumed Al-Farghani used Roman miles, when, in fact, he’d used the longer Arabic miles, not the shorter Roman miles. This error reduced the circumference of the globe by about 25%. This smaller estimate was more to Columbus’ taste. He wanted the earth to be smaller, to make the voyage feasible (and making it easier to convince investors to fund the expedition).
Wedding portrait of King Ferdinand of Aragon and Queen Isabella of Castile, 15th century, anonymous.
Columbus also relied on a map by Paolo dal Pozzo Toscanelli, a fellow Italian who underestimated the Earth's circumference and overestimated the size of Asia. Together, these two errors artificially shrank the Atlantic Ocean, making the journey seem short enough for ships to survive without restocking provisions. [3]
The Investors
At the time, the only investors who could underwrite such a voyage were monarchs. First, Columbus tried to interest King John II of Portugal in financing the expedition. Unfortunately for Columbus, King John sent the proposal to his maritime committee which rejected it because they believed the calculations were wrong (i.e. the earth was much larger than Columbus proposed), and the King was already heavily invested in reaching India by sailing around the southern tip of Africa (which Vasco de Gama succeeded in doing a few years later).
So, in 1486, Columbus moved on to Isabella and Ferdinand of Spain. The Spanish treasury was cash-strapped due to recent wars, and Columbus worked for years to convince Isabella that this proposed trip to India would replenish treasury funds. She finally relented and ordered the town of Palos to pay a fine by building two ships, the Nina and the Pinta. The Santa Maria was provided by its owner and captain.
Unfortunately, they had some difficulty finding sailors willing to make the trip – most thought it meant certain death. Isabella then pardoned criminals who agreed to go.
Landfall
Waldseemüller map from 1507 is the first map to include the name "America" and the first to depict the Americas as separate from Asia. There is only one surviving copy of the map, which was purchased by the Library of Congress in 2001 for $10 million.
On August 3, 1492, the three ships left Palos with a total of 87 men, with Columbus as the navigator. The trip was difficult, and food was moldy and running low. The crews were close to mutiny when, on October 12, land was sighted. Columbus thought he’d found India, but in reality it was the Caribbean island of Guanahani, which Columbus promptly renamed San Salvador.
The ships re-stocked by trading with local people, and continued sailing around the Caribbean, looking for India. They found Cuba (which Columbus suggested was China), and named other islands after his ship and the Spanish monarchs: La Isla de Santa María de Concepción (Rum Cay), Fernandina (Long Island), and Isabella (possibly Samana Cay).
Columbus made a total of four voyages to “India”, the last one discovering Central America, and ending in 1504. Through it all, he continued to insist that the New World was part of the far east. He had financial incentive to do so, because his original contract declared him Admiral of the Ocean Sea and the Viceroy and Governor over any lands he discovered – but only in India and the far east.
Eventually, other explorers revealed the truth in more accurate maps. In 1509 Amerigo Vespucci wrote a letter to his patron Lorenzo di Pierfrancesco de' Medici declaring the existence of a new world beyond the Atlantic which bear his name to this day: America.
Today, Global Positioning Systems (GPS) give us centimeter-level or even millimeter-level precision of our location on the earth. Since 1972, Berntsen has helped surveyors mark points precisely with a full range of high-quality and durable products that stand the test of time.