What are latitude and longitude?

Quick answer

Latitude and longitude are the two angular coordinates used to locate any point on Earth. Latitude measures how far north or south a point is from the equator; longitude measures how far east or west it is from the prime meridian. Coordinates are written in degrees and commonly formatted either as degrees/minutes/seconds or as decimal degrees, and they depend on an underlying geodetic datum for precise positioning.

How latitude and longitude work

Think of geographic coordinates as a global grid drawn on a roughly spherical Earth. Lines of latitude (parallels) circle the globe east-west and indicate north-south position. Lines of longitude (meridians) run from pole to pole and indicate east-west position.

Latitude values range from 0 at the equator to 90 degrees at the poles; longitude values range 180 degrees east to 180 degrees west relative to the prime meridian. Together a latitude and a longitude pair pinpoints a single location on the surface.

Coordinate formats you will encounter

Maps, GPS devices and online services use two common formats. One is degrees, minutes, seconds, abbreviated DMS. The other is decimal degrees, often used by software and GPS devices because it is simple to compute with.

Degrees, minutes, seconds (DMS)

In DMS, each degree is divided into 60 minutes and each minute into 60 seconds. A coordinate looks like 40° 26' 46" N, 79° 58' 56" W. That format is compact for human reading but requires conversion for many calculations.

Decimal degrees

Decimal degrees express the same values as a single number with a decimal point, for example 40.4461, -79.9822. Positive and negative signs indicate hemisphere: latitude positive in the northern hemisphere, negative in the southern; longitude positive east of the prime meridian, negative west.

For a practical guide to reading coordinates on devices or converting between formats, see Read GPS coordinates.

Converting between DMS and decimal degrees: a step-by-step example

Below is a clear conversion process you can follow by hand or in a spreadsheet. This is a worked example so you can check your own conversions.

1. Start with a DMS coordinate: 34° 3' 30" N, 118° 14' 37" W.
2. Convert each component to decimal: decimal degrees = degrees + (minutes/60) + (seconds/3600).
3. Latitude: 34 + (3/60) + (30/3600) = 34.058333... so write 34.058333 (north is positive).
4. Longitude: 118 + (14/60) + (37/3600) = 118.243611... west means negative, so write -118.243611.
5. The final decimal coordinate is 34.058333, -118.243611.

For a deeper comparison of notation and when to use each format, see Degrees, Minutes, Seconds vs Decimal Degrees.

Why geodetic datums matter

Latitude and longitude angles are measured against a mathematical model of Earth called a datum. A datum defines the size and shape of the reference ellipsoid and the origin for the coordinate system. Using different datums shifts coordinates by meters to hundreds of meters, which matters for surveying, mapping and precise navigation.

GPS receivers and commercial maps commonly use the WGS84 datum; other systems like NAD83 are still used for regional mapping. If you record coordinates in one datum and plot them against a map using another, the point may appear in the wrong place. For an explanation of common datums, see Why datums matter.

Using coordinates with GPS and maps

Modern GPS units display coordinates in a selectable format and datum. Before you navigate, confirm three settings: coordinate format (DMS or decimal), datum (WGS84 is a common default), and the hemisphere sign convention if using decimal degrees.

• Set your GPS to the same datum and coordinate format you plan to record or share.
• When entering coordinates into apps, pay attention to whether the app expects north/south and east/west letters or signed decimals.
• For sharing with others, include the datum and the coordinate format to avoid ambiguity.

If you need a short how-to for reading device outputs or converting values for navigation, consult Read GPS coordinates and the note on projections below.

Map projections and the prime reference lines

Latitude and longitude are geographic coordinates, not map coordinates. When you place the curved Earth on a flat map, a projection is used and distances and shapes can be distorted. That is why mapmakers choose projections with certain properties depending on purpose.

For more on the baseline reference lines used to measure latitude and longitude, see Map projections explained.

Common mistakes and a checklist before you record coordinates

Many coordinate errors are avoidable. Below are common mistakes and a practical checklist to use in the field.

• Mixing formats: entering DMS into a field that expects decimal degrees will produce nonsense.
• Wrong sign or hemisphere: forgetting negative longitude for west can place a point on the opposite side of the planet.
• Datum mismatch: plotting WGS84 coordinates onto a map in a different datum can shift location by tens of meters or more.
• Insufficient precision: rounding too early can make a difference, especially in surveying or search-and-rescue.

Field checklist before sharing or saving coordinates:

1. Confirm coordinate format and datum on your device.
2. Record both format and datum when you copy coordinates.
3. Keep at least five decimal places for decimal degrees when high precision is required (for general hiking three to four decimals is often sufficient).
4. Test a entered coordinate on a map to verify it lands where you expect.

When to use each format and practical tips

Use DMS in human-readable text, historic charts, and when quoting coordinates from older sources. Use decimal degrees when inputting coordinates into GPS units, mapping software, or spreadsheets. When precision and legal definitions matter, always record the datum used.

For students and map users, a simple rule is: record the full coordinate pair, state the format and datum, and double-check by plotting on a reliable map before you rely on the point for navigation.

Closing

Latitude and longitude are straightforward in principle — two angles that identify a point on Earth — but in practice you must pay attention to format and datum to avoid errors. Follow the conversion steps and checklist above when you read, record or share coordinates. If you want step-by-step conversion tools or device instructions, consult Read GPS coordinates and the primer on Degrees, Minutes, Seconds vs Decimal Degrees, and review Why datums matter before precision work.