Understanding Latitude and Longitude

Latitude and longitude form a coordinate system to locate any place on Earth.
Latitude lines run horizontally, and longitude lines run vertically, forming a grid.
These lines are measured in degrees.

Latitude measures the angular distance in degrees north or south from the Equator.
The Equator is 0° latitude.
Latitude lines, also known as parallels, run parallel to each other.
The latitudes of the North and South Poles are 90° N and 90° S, respectively.
Important lines of latitude:
- Equator: 0°
- Tropic of Cancer: 23.5° N, the most northerly latitude where the Sun can appear directly overhead at noon.
- Tropic of Capricorn: 23.5° S, the most southerly latitude where the Sun can appear directly overhead at noon.
- Arctic Circle: 66.5° N, the southernmost latitude in the Northern Hemisphere where the Sun can remain continuously above or below the horizon for 24 hours.
- Antarctic Circle: 66.5° S, the northernmost latitude in the Southern Hemisphere where the Sun can remain continuously above or below the horizon for 24 hours.
Low latitudes are near the Equator, between 0° and 30° N/S.
Mid-latitudes are between 30° and 60° N/S.
High latitudes are near the poles, between 60° and 90° N/S.
One degree of latitude is approximately 111 kilometers (69 miles).
In geographic coordinates, latitude is always stated first.

Longitude measures the angular distance in degrees east or west from the Prime Meridian.
The Prime Meridian is 0° longitude.
Longitude lines are also known as meridians.
Meridians converge at the North and South Poles.
The maximum longitude is 180°, which is the International Date Line.
The International Date Line (180°) marks the change of one calendar day when crossed.
Longitude is used to calculate time differences around the world.
Each 15° of longitude corresponds to a one-hour time difference.
In geographic coordinates, Longitude is stated second.

The Prime Meridian represents 0° longitude, the starting point for measuring distance east and west around Earth.
The Prime Meridian passes through Greenwich, England.
It was established in 1884 at the International Meridian Conference.
The Prime Meridian serves as the reference point for time zones worldwide.

Latitude and longitude are measured in degrees (°), minutes (’), and seconds (").
One degree is divided into 60 minutes.
One minute is divided into 60 seconds.
A location's coordinates can be specified with great precision.
Example: 40° 26' 46" N, 79° 58' 56" W.

Latitude and longitude together form a geographic coordinate system.
This system allows any location on Earth to be uniquely identified.
Different datums are used, which are reference systems that define the size and shape of the Earth.
The most common datum used today is WGS 84 (World Geodetic System 1984).
Older datums include NAD27 (North American Datum 1927) and NAD83 (North American Datum 1983).

A great circle is the largest circle that can be drawn around a sphere.
The Equator is a great circle.
Meridians, when paired with their opposite meridian, form a great circle.
The shortest distance between two points on Earth is along a great circle route.
Airlines often use great circle routes to save fuel and time.

Latitude is determined by measuring the angle of the sun or stars above the horizon.
Longitude requires a precise measure of time compared to the time at the Prime Meridian.
Historically, determining longitude was a major challenge for navigators.
The invention of accurate clocks (chronometers) in the 18th century solved the problem of finding longitude at sea.

GPS (Global Positioning System) uses satellites to determine latitude, longitude, and altitude.
GPS provides very accurate location information.
Digital maps and GIS (Geographic Information Systems) rely on latitude and longitude coordinates.
Online mapping services like Google Maps use latitude and longitude.