# What Is Latitude? > Latitude tells how far north or south a place lies on Earth. It is an angle measured from the equatorial plane, not a mileage read directly along the ground. A latitude can identify an entire east-west line, so a second coordinate is... Canonical URL: https://www.argo.net/what-is-latitude/ Byline: ARGO.net Editorial Team Published: 2026-09-03T12:28:26+00:00 Categories: Earth, Explainer ![A globe marked with geographic coordinate lines](https://www.argo.net/wp-content/uploads/2026/09/argo-wave21-53588-pexels-335394.jpg) Latitude tells how far north or south a place lies on Earth. It is an angle measured from the equatorial plane, not a mileage read directly along the ground. A latitude can identify an entire east-west line, so a second coordinate is needed to locate one point. On maps and globes, latitude appears as a family of parallel circles. NOAA's explanation of [latitude and its measurement](https://oceanservice.noaa.gov/facts/latitude.html) begins with the equator at zero degrees and reaches 90 degrees at either pole. The coordinate looks simple because its values fit within a familiar range. Precision is more demanding. Surveyors must state the reference model of Earth and the datum that connects a numerical latitude to a physical location. Rounding also carries a physical consequence. Removing decimal places shifts the implied position by meters or kilometers, depending on how many digits are discarded. ## Latitude is an angle centered on the equator The **equator** is the great circle halfway between the geographic poles. Its plane passes through Earth's center and stands perpendicular to the rotation axis. Latitude describes angular displacement north or south of that plane. Lines joining places with the same latitude are called **parallels**. Except for the equator, each is a smaller circle. Their east-west appearance on common maps can suggest that they are distances, but the coordinate itself remains angular. A location at 40 degrees north lies north of the equator by the stated angle. The notation must include N or S unless a sign convention is clearly used. In signed decimal form, northern values are commonly positive while southern values are negative. Latitude does not specify east-west position. Every point on a parallel shares the same latitude. Longitude supplies the other horizontal coordinate, while height may be added when a three-dimensional position is required. **Coordinate order** must be stated because software conventions differ. Reversing the pair can move a mapped feature to another continent or produce an invalid value. ## Degrees can be divided in two common ways Traditional notation divides one degree into 60 **minutes of arc**, then divides each minute into 60 seconds. A coordinate might therefore state degrees followed by minutes and seconds. The symbols resemble time notation but describe angle. Digital systems often use decimal degrees. Converting requires dividing minutes by 60 and seconds by 3,600 before adding them to the whole degrees. A southern coordinate retains its direction or receives a negative sign. Mixing formats can produce large errors. The value 30 degrees 30 minutes is 30.5 decimal degrees, not 30.30. Navigation software may accept several formats, so users should confirm the expected input before entering a position. Hemisphere notation also deserves attention. A negative sign combined with an S label can be interpreted inconsistently if software is not designed to accept both. ## One degree is close to 111 kilometers The north-south distance represented by a degree of latitude is roughly 111 kilometers, or about 69 miles. A minute is approximately one nautical mile. A second represents about 31 meters, though exact values vary because Earth is not a perfect sphere. Six decimal places in a coordinate may suggest submeter resolution, but the number of displayed digits is not proof of positional accuracy. The **nautical mile** is now defined as exactly 1,852 meters. Its historical relationship to a minute of latitude remains useful for understanding marine charts, but survey work uses the exact modern definition rather than treating every minute on Earth as identical. Latitude spacing changes slightly from equator to pole on an ellipsoidal Earth. The difference is small on a classroom globe but significant in precision geodesy. Calculations therefore use an Earth model appropriate to the coordinate system. The length of a degree increases modestly toward the poles. Distance tools account for that change rather than applying one conversion everywhere. Map scale adds another complication. A projection transforms the curved surface onto a plane and can stretch distances. Parallels may look evenly spaced on one map even when its scale varies. Measurements should follow the projection rules shown for that map. The [U.S. Geological Survey overview of map projections](https://www.usgs.gov/programs/national-geospatial-program/science/map-projections) explains why every flat map introduces distortion. Latitude survives as a coordinate, but its visual spacing depends on the chosen projection. ## Five named parallels have astronomical meanings The Tropics of Cancer and Capricorn mark the most northerly and southerly latitudes where the Sun can appear directly overhead at local noon. Their positions are tied to Earth's axial tilt. They lie near 23.4 degrees north and south. The Arctic and Antarctic Circles lie near 66.6 degrees. Poleward of them, continuous daylight or darkness can last for at least one full day each year. The exact values change slowly as Earth's tilt varies. These named lines are useful geographic references, not walls between uniform climate zones. Elevation and ocean circulation also influence conditions at a given latitude. ## People measured latitude long before satellites In the Northern Hemisphere, navigators could estimate latitude from the altitude of Polaris above the horizon. Near the equator and across the Southern Hemisphere, they instead observed the Sun or selected stars. Published tables accounted for the date. Instruments such as the sextant measure the angle between a celestial body and the horizon. A correct sight still needs time information and mathematical corrections. The [Smithsonian's account of celestial navigation](https://timeandnavigation.si.edu/multimedia-asset/celestial-navigation-at-sea) describes how mariners combined observations with published data. Refraction changes the apparent altitude near the horizon and the observer's height affects the visible horizon. Navigation tables provide corrections for these known effects. Modern receivers derive coordinates from satellite signals. Surveyors seeking centimeter-level results also use fixed reference stations and carefully processed observations. A phone's displayed latitude is convenient, but its uncertainty is not the same as a geodetic survey. NOAA's [Continuously Operating Reference Stations network](https://geodesy.noaa.gov/CORS/) provides satellite tracking data tied to the national reference system. The network helps users connect local measurements made at different times to a consistent frame. ## Geodetic and geocentric latitude are not identical Earth is slightly flattened at the poles, so geodesists approximate it with an oblate ellipsoid. **Geodetic latitude** is defined by a line perpendicular to that reference ellipsoid. It is the latitude used in ordinary mapping systems. **Geocentric latitude** uses a line from the point to Earth's center. Away from the equator and poles, that line is not quite the same as the ellipsoid normal. The difference can exceed a tenth of a degree at some latitudes. Astronomers and geophysicists may need the distinction when calculating directions relative to Earth's center rather than its reference surface. A coordinate also belongs to a datum. NOAA's [description of horizontal datums](https://geodesy.noaa.gov/datums/horizontal/) explains how a reference frame assigns coordinates to positions on Earth. Two datums can give slightly different numbers for the same monument. The shift may be modest on a regional map yet large enough to misplace a surveyed boundary or monitoring instrument. Latitude is therefore both an intuitive geographic idea and a precise technical quantity. In everyday use, it states a place's position relative to the equator. For surveying, the number is complete only when its format, datum and uncertainty are known. A reliable coordinate record also keeps the original precision instead of adding digits during later formatting. **Coordinate metadata** protect the meaning of the number when it moves between maps or databases. They allow another analyst to transform the coordinate correctly and evaluate its accuracy for a new purpose. The record can then be traced to the measurement system that produced it, even years after the original fieldwork. **Related reading:** [where the horse latitudes lie](https://www.argo.net/what-are-the-horse-latitudes/) and [the geodetic meaning of sea level](https://www.argo.net/is-sea-level-the-same-everywhere/). **Related reading:** [where the horse latitudes lie](https://www.argo.net/what-are-the-horse-latitudes/) and [the geodetic meaning of sea level](https://www.argo.net/is-sea-level-the-same-everywhere/). **Explore this topic:** [What Is Longitude?](https://www.argo.net/what-is-longitude/) and [How Long Does It Take to Make a Nautical Chart?](https://www.argo.net/how-long-does-it-take-to-make-a-nautical-chart/).