Greenwich Meridian – Concept, history and the equator

We explain what the Greenwich meridian is and what is the history of this imaginary line. Also, how the equator is located.

Greenwich Meridian
The Greenwich meridian marks the world standard base time.

What is the Greenwich meridian?

It is known as the Greenwich meridian, but also the zero meridian, the base meridian or the prime meridian, at the imaginary vertical line that divides the world map in two identical halves and from which the lengths are measured. It is, in addition, the meridian that marks the world standard base time, to which (GMT +) are added or (GMT-) hours are subtracted to determine the time bands of the planet.

The location of this imaginary line gets its name because traverses the British town of Greenwich, in England, and because there it was in the Royal Observatory of Greenwich, built in 1675. However, the imaginary line crosses several countries as it passes, and it is common to find in the United Kingdom, France, Spain, Algeria, Mali, Burkina Faso , Ghana, Togo and Antarctica signs that mark your location.

This central meridian, whose crossing with the line of the equator divides the globe into four regions, it is important in matters of geography and navigation, since it allows the existence of a coordinate network that allows encrypting a location in degrees and minutes.

Thus the Greenwich meridian divides the planet into two semicircles of 180 ° each, segmented into time zones of 15 ° each (result of dividing 360 ° of the complete circumference by 24 hours).

In addition, the universal day (solar time) begins by convention at midnight in Greenwich, since the opposite line on the other side of the planet is considered the International Date Line.

History of the Greenwich meridian

The adoption of this meridian as the basis for the time and coordinate system was taken in 1884 in Washington DC, United States, at a convention attended by delegates from 25 countries.

There the universalization of this system was agreed, since different meridians were used as a guide in various places. The resolution had the disapproval of countries such as the Dominican Republic and the abstentions of France and Brazil, but it was eventually imposed throughout the world to date.

There is a very slight angular difference (5.3 seconds) between the Greenwich meridian and the reference meridian used by contemporary GPS systems, due to the fact that 1958 the first Global Positioning Satellite system was launched, whose greater precision in the determination of the 0 ° fixed them about 102 meters to the east of the meridian of Greenwich.


The equator divides the Earth into north and south.

The equator is another imaginary line, which divides planet Earth into two separate hemispheres: the north and the south, each one with a different celestial vault. This line allows the tracing no longer of the meridians, but of the lines of latitude, the parallels. In this sense, the equator would be the zero parallel or base parallel, whose circular shape traces the earth’s circumference in the tropics.

The equator crosses the territories of Ecuador (whose name comes precisely from this line), Colombia, Brazil, São Tomé and Príncipe, Gabon, Republic of the Congo, Democratic Republic of the Congo, Uganda, Kenya, Somalia, Maldives (although not by its islands), Indonesia (the islands of Sumatra, Borneo, Sulawesi and Halmahera) and Kiribati.

The regions in which the parallels divide the earth from the equator are known as climatic fringes, and mark the beginning and end of the tropical, temperate and polar zones of the planet.

Latitude and longitude

Greenwich Meridian
Latitude and longitude traverse the Earth from north to south and from east to west.

Latitude and longitude are the components of the coordinates of the navigation system of planet Earth used, among other things, for maps and for satellite or GPS positioning.

These are two sets of imaginary lines that traverse the globe from north to south and from east to west, sectioning the surface of the planet in a regular grid, whose base axes are the Greenwich meridian (longitude 0) and the equator (latitude 0).

Using latitude and longitude, the Geographic Coordinates (latitude, longitude) of a certain point on the planet’s surface can be set, for example: Spain is located at the coordinates O 4 °, 0’00 ”(West four degrees, zero minutes , zero seconds) of longitude and N 40 °, 0’00 ”(North forty degrees, zero minutes, zero seconds).