A physical marker of the historic Greenwich Meridian at the Royal Observatory.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

Spherical coordinates. lines and marker enlarged for clarity.

Latitude 51.5° · longitude -0.1° · local mean solar-time difference -0.01 h from Greenwich. Gold arc measures latitude from the equator; blue arc measures longitude from Greenwich. This does not select a civil time zone.

Graticule and coordinates

Use latitude and longitude to locate a point on Earth, and relate longitude to differences in local solar time.

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Why it happens

Latitude measures an angle north or south of the equator, while longitude measures an angle east or west of the prime meridian. Parallels and meridians form the coordinate grid called the graticule.

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The historic Greenwich Meridian makes a reference longitude tangible. Modern WGS84 zero longitude lies about 102 metres east of this line.

Try a comparison

Change Latitude first, then Longitude. Read the hemisphere letters and explain why changing one coordinate moves the marker along a different direction.

Reading the result

These are angular coordinates on a sphere; a degree of longitude covers less ground as latitude increases.

A common misunderstanding

The coordinates 0 degrees latitude and 0 degrees longitude locate Greenwich.

Greenwich is close to zero longitude but about 51.5 degrees north of the equator. Zero latitude lies on the equator, so the two zero coordinates meet in the Gulf of Guinea. Latitude and longitude identify separate angular directions and must both be specified.

Cases

Exam language

Graticule

The network of meridians and parallels on a globe or map.

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NASA Blue Marble monthly composite in an equirectangular latitude–longitude grid. Latitude measures angular distance north or south of the equator; parallels run east–west. The geographic reference lines are mathematical, not marks on the land.

Meridian

A line of longitude running from one pole to the other. A place’s local solar noon occurs when the Sun crosses its local meridian. Meridians meet at the poles, so the distance between adjacent longitudes decreases towards high latitudes.

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The historic Greenwich Meridian makes a reference longitude tangible. Modern WGS84 zero longitude lies about 102 metres east of this line.

Parallel

A line joining places at the same latitude. On a spherical globe, the equator is the largest parallel and the others become smaller towards the poles. Parallels do not intersect, unlike meridians of longitude, which meet at the poles.

Latitude

The angular position of a place north or south of the equator, expressed in degrees. Latitude helps determine solar altitude and seasonal day length. Lines of equal latitude are parallels, unlike meridians, which measure longitude.

Longitude

The angular position of a place east or west of the prime meridian, expressed up to 180 degrees. Earth turns through approximately 15 degrees per hour, linking longitude with local solar time. Civil time zones also reflect administrative choices.

Prime meridian

The chosen zero of longitude. The modern reference meridian used by WGS84 lies about 102 m east of the historic Greenwich transit circle.

Equator

The circle at zero degrees latitude, halfway between the poles. It divides Earth into Northern and Southern Hemispheres. It is a parallel of latitude, whereas meridians of longitude run from pole to pole.

International Date Line

The conventional boundary across which the civil calendar date changes, located broadly near 180 degrees longitude. Its course bends around countries and islands for practical reasons. It differs from the prime meridian, which defines zero longitude.

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Landsat 8, 6 June 2017: Big Diomede (the larger island, left) belongs to Russia and Little Diomede (right) to the US. The International Date Line passes through the water between them; it is a convention, not a visible physical feature.

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Latitude51.5°Longitude-0.1°