Cartographers have divided up the Earth into a grid of imaginary lines that run both north and south (latitude) and east and west (longitude).
Zero degrees latitude is the line designating the Equator and divides the Earth into two equal hemispheres (north and south).
Zero degrees longitude is an imaginary line known as the Prime Meridian.
Mapping the Location of Zero Degrees Latitude and Zero Degrees Longitude
Therefore, we are looking for what exists at the location where the Equator and the Prime Meridian cross each other. In other words, we are want to what is located at the confluence of (0°N 0°E)
If you look at the intersection of 0 degrees latitude (known as the Equator) and 0 degrees longitude (known as the Prime Meridian) on a map, you will see that the confluence falls in the middle of the Atlantic Ocean, in the Gulf of Guinea off the coast of western Africa.
The map below shows in dashed red the lines of zero degrees latitude and zero degrees longitude.
The closest country to 0°, 0° is the African country of Ghana which lies about 614 km (382 mi) to the north of this confluence.
The closest piece of land to 0°, 0° is a small islet offshore of Ghana, between Akwidaa and Dixcove at the latitude and longitude coordinates of 4°45′30″N, 1°58′33″W. The distance from this islet to 0°, 0° is about 570 km (354.2 mi).
Therefore, the open ocean lies at zero degrees latitude and zero degrees longitude.
This coordinate is marked by a weather observation buoy (Station 13010—Soul), placed there as part of the Prediction and Research Moored Array in the Atlantic, also known as PIRATA and is operated by the countries of United States, France, and Brazil.
There is a fictional island known as Null Island at zero latitude and zero longitude. Although it’s not clear when the concept of Null Island was conceived, it came to prominence with the release of public domain Natural Earth GIS data. This one square meter area island is used for troubleshooting purposes for flagging geocoding failures, which is geographic data that cannot be properly located due to an error.
When a GIS software program or other mapping tools are unable to properly assign geographic coordinates to an address, the address record might be assigned a coordinate of 0,0 so cartographers can flag those address with errors.
Learn more: Null Island: Where Geocoding Errors Go to Live