Introduction to Geography, Earth’s Shape, and the Coordinate System

If someone asked you to point to a precise spot on our planet, how would you do it? The answer lies in a system that the entire world agreed upon over a century ago. But before we get to that system, we first need to understand what geography actually is, and what shape this planet of ours truly has.

What Geography Studies: A Subject Without Boundaries

The word geography comes from Greek roots: “geo” meaning earth and “graphia” meaning description. The Greeks were the first civilisation to study the earth in a structured way, making them the world’s earliest geographers.

Eratosthenes, one of the most important early geographers, defined geography as the study of the earth as the home of man. This is a deceptively simple definition with a powerful implication: since human life unfolds on the surface of the planet, the primary focus of geography is the surface of the earth.

What makes geography unusual as a subject is that it has no fixed boundary in terms of what it can study. It covers natural phenomena, human societies, economies, climates, landforms, and much more. So what holds it all together? The answer is spatial analysis (the study of things in relation to space and location). Geography is governed by a method rather than by a specific body of knowledge. That method is spatial analysis: examining the process, the why, the how, and the dimensions of anything in relation to where it occurs.

A few important related terms to know early on:

• Geopolitics (the geographical causation of international politics) examines how location, terrain, and resources shape the power dynamics between nations
• Bunge, a notable geographer, observed that “science is a deadly enemy of uniqueness.” What he meant is that science identifies order, patterns, and regularities in the world, turning what seems complex or unique into something understandable and predictable
• Geodesy (the science that determines Earth’s shape and size) relies on surveys and mathematical calculations to give us the precise measurements that maps and navigation systems depend on

How Our Understanding of Earth’s Shape Evolved

For a long time, people assumed the earth was a perfect sphere. This spherical perfection model was one of the basic assumptions of geodesy for centuries.

That changed in 1687, when Sir Isaac Newton argued that the earth and other spinning planets could not be perfectly spherical. His reasoning was straightforward: the rotation of the earth pushes material outward at the middle, causing a slight bulge at the equator, while the poles get slightly compressed and flattened. This shape, wider at the middle and flatter at the top and bottom, is called an oblate spheroid (a sphere that is slightly squashed along its vertical axis).

Today, scientists describe the earth as a geoid. The term literally means “earth-shaped.” It acknowledges that our planet’s true shape is not a perfect sphere, not a perfect ellipsoid, but something uniquely its own, with subtle irregularities across its surface.

Here are the key measurements that capture this shape:

Measurement	Value
Polar diameter (slightly flattened)	~12,714 km
Equatorial diameter (slightly bulging)	~12,756 km
Difference	~42 km
Percentage variation from a perfect sphere	~0.3%

The calculation for percentage variation is:

$\frac{12{,}756 - 12{,}714}{12{,}756} \approx 0.3\%$

That 0.3% difference is remarkably tiny. For most practical purposes, the earth can be treated as if it were a perfect sphere. In fact, the earth is a more perfect sphere than most spherical objects we handle in daily life, such as basketballs or footballs, which have far greater surface irregularities relative to their size.

The International Meridian Conference of 1884: One World, One System

Before 1884, the world had no shared system for measuring location or time. Every region used its own local references and its own local clocks. This created enormous confusion for shipping, trade, communication, and science.

To solve this, the International Meridian Conference (IMC) was held in October 1884 in Washington, D.C., at the request of U.S. President Chester A. Arthur. Forty-one delegates from 25 nations gathered with one goal: to agree on a single prime meridian (the starting line for measuring longitude) that the whole world would use.

The conference chose the Greenwich Meridian as the Prime Meridian of the World, fixing it at $0°$ longitude. Along with this, the conference also established the concepts related to standardised time zones and the International Date Line (IDL), which sits at $180°$ east and west of Greenwich.

The Latitude-Longitude Grid: Pinpointing Any Location on Earth

One of the most fundamental tasks in geography is being able to state the exact position of any spot on the planet. This requires a comprehensive and logical framework, and that framework is the imaginary grid system: a network of parallels (horizontal lines) and meridians (vertical lines) that covers the entire globe.

This grid is anchored by three natural reference features determined by Earth’s oblate shape: the North Pole, the South Pole, and the equator.

Latitude is the angular distance of a place measured north or south of the equator. The lines connecting all points at the same latitude are called parallels. Latitude ranges from $0°$ at the equator to $90°$ N at the North Pole and $90°$ S at the South Pole.

Longitude is the angular distance between the meridian passing through a given point and the Greenwich Meridian ($0°$). The lines running from pole to pole at a given longitude are called meridians. Longitude ranges from $0°$ at Greenwich to $180°$ in both the eastern and western directions.

Together, these two values let you describe any point P on Earth’s surface as P(latitude, longitude). For example, a point at $28°$ N latitude and $77°$ E longitude is written as P($28°$N, $77°$E).

Why Greenwich Became the World’s Prime Meridian

The choice of Greenwich was not random. Four practical reasons made it the strongest candidate:

• Already in use by sailors — The Royal Observatory at Greenwich had been serving as a navigational reference point for sailors long before 1884. Choosing it simply formalised existing practice
• British naval and imperial dominance — At the time, the British Empire was the world’s leading maritime and colonial power, and British charts and navigation already used Greenwich as the reference
• Convenient placement of the International Date Line — Setting Greenwich at $0°$ placed the $180°$ meridian (the basis for the IDL) in the middle of the Pacific Ocean, where day-night transitions would affect the fewest people
• The opposite meridian runs through ocean — The meridian directly opposite Greenwich ($180°$) passes largely through open ocean, meaning the abrupt calendar date change happens far from major population centres