Geographic Grid: Latitudes & Longitudes

Thirty vocabulary flashcards covering core terms and definitions related to Earth’s geographic grid, latitudes, longitudes, time calculations, and Great Circles.

Geographic Grid

A network of imaginary latitude and longitude lines whose intersections pinpoint exact locations on Earth.

Latitude

Angular distance north or south of the Equator, measured in degrees (0°–90°).

Longitude

Angular distance east or west of the Prime Meridian, measured in degrees (0°–180°).

Equator

The 0° latitude; the only latitude that is a Great Circle and divides Earth into Northern and Southern Hemispheres.

Prime Meridian

The 0° longitude line passing through Greenwich, used as the global reference for time and position.

Parallels of Latitude

Imaginary east–west lines parallel to the Equator; they never meet and decrease in length toward the poles.

Meridians of Longitude

Imaginary north–south semicircles converging at the poles; all are equal in length and form Great Circles when paired with their opposite meridian.

Main Latitudes

Key named parallels: Equator (0°), Tropic of Cancer (23.5° N), Tropic of Capricorn (23.5° S), Arctic Circle (66.5° N), Antarctic Circle (66.5° S), and the poles (90° N/S).

Tropic of Cancer

The 23.5° N latitude marking the northern limit of the sun’s overhead position.

Tropic of Capricorn

The 23.5° S latitude marking the southern limit of the sun’s overhead position.

Arctic Circle

The 66.5° N latitude that outlines the northern polar region and defines the North Frigid Zone boundary.

Antarctic Circle

The 66.5° S latitude that outlines the southern polar region and defines the South Frigid Zone boundary.

Northern Hemisphere

The half of Earth lying north of the Equator.

Southern Hemisphere

The half of Earth lying south of the Equator.

Torrid Zone

The hottest climatic zone between the Tropic of Cancer and Tropic of Capricorn.

Temperate Zones

Moderate-climate belts lying between each tropic and its corresponding polar circle (23.5°–66.5° in each hemisphere).

Frigid Zones

Cold polar regions located between each polar circle and the respective pole.

Great Circle

Any circle drawn on a sphere whose center and radius are the same as the sphere’s; represents the shortest distance between two points.

Small Circle

A circle on a sphere that does not share the sphere’s center; all latitudes except the Equator are small circles.

Absolute Location

A place’s exact position described by precise latitude and longitude coordinates.

Local Time

Time at a specific longitude determined by the sun’s position; varies 4 minutes per degree of longitude.

Standard Time

Uniform time for an entire region, based on a chosen central meridian to avoid local-time confusion.

Time Zone

One of 24 global bands, each spanning about 15° of longitude and sharing a common standard time.

Greenwich Mean Time (GMT)

Standard reference time at 0° longitude; basis for calculating world time zones.

Indian Standard Time (IST)

India’s official time, set 5 hours 30 minutes ahead of GMT on the 82° 30′ E meridian.

International Date Line (IDL)

A largely 180° longitude line where calendar dates change; crossing eastward loses a day, westward gains a day.

EGA-WLS Formula

Mnemonic for time correction: East – Gain – Add minutes; West – Lose – Subtract minutes (4 per degree).

Longitude–Time Relationship

Rule that Earth’s 360° rotation in 24 h means 15° = 1 h or 1° = 4 min time difference.

Great Circle Route

The shortest navigational path between two distant points on Earth, lying along a Great Circle arc.

180° Meridian

The longitude directly opposite the Prime Meridian; forms a full Great Circle with 0° and underlies the IDL.