Geographic Grid: Latitudes and Longitudes

Vocabulary flashcards summarizing key definitions and concepts from Chapter 2 on the geographic grid, latitudes, longitudes, time calculation, heat zones, and great circles.

Geographic Grid

The network of intersecting lines of latitude and longitude used to pinpoint any location on Earth.

Latitude

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

Lines of Latitude (Parallels)

Imaginary east–west circles parallel to the Equator; only the Equator is a Great Circle.

Longitude

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

Meridian

A line of longitude; all meridians converge at the poles and are semicircles of equal length.

Prime Meridian

The 0° meridian passing through Greenwich, London; the starting point for measuring longitude and time.

Equator

The 0° latitude line that divides Earth into Northern and Southern Hemispheres and forms a Great Circle.

Great Circle

Any circle on Earth whose plane passes through the planet’s center; represents the shortest distance between two points.

Small Circle

A circle on Earth whose plane does not pass through the planet’s center; all parallels except the Equator are small circles.

Great Circle Route

The shortest path between two places, lying along an arc of a Great Circle (e.g., New York–Moscow over the pole).

Tropic of Cancer

Latitude 23½° N marking the northern limit of the Tropics.

Tropic of Capricorn

Latitude 23½° S marking the southern limit of the Tropics.

Arctic Circle

Latitude 66½° N; boundary of the North Polar (Frigid) Zone.

Antarctic Circle

Latitude 66½° S; boundary of the South Polar (Frigid) Zone.

North Pole

Point at 90° N latitude where all longitudes meet.

South Pole

Point at 90° S latitude where all longitudes meet.

Northern Hemisphere

Half of Earth lying north of the Equator.

Southern Hemisphere

Half of Earth lying south of the Equator.

Eastern Hemisphere

Half of Earth east of the Prime Meridian up to 180°.

Western Hemisphere

Half of Earth west of the Prime Meridian up to 180°.

Torrid (Tropical) Zone

Region between the Tropic of Cancer and Tropic of Capricorn; hottest heat belt.

Temperate Zones

Regions between 23½° and 66½° in each hemisphere; climate generally moderate.

Frigid Zones

Polar regions between 66½° and 90° in each hemisphere; very cold temperatures prevail.

Absolute Location

Exact position of a place given by its latitude and longitude coordinates.

Distance per Degree of Latitude

Approximately 111 km; used to estimate north–south distances (e.g., 19° ≈ 2,109 km).

Convergence of Meridians

Spacing between longitudes decreases from 111 km at the Equator to 0 km at the poles.

Longitude–Time Relationship

Earth rotates 360° in 24 h → 15° per hour → 1° every 4 minutes.

EGA–WLS Rule

East – Gain – Add; West – Lose – Subtract when converting longitude difference to time difference.

Local Time

Time at a place determined by the sun’s position at its meridian (noon when the sun is overhead).

Time Zone

One of 24 longitudinal belts (~15° wide) sharing the same standard time.

Standard Time

Official time for a region set by its central meridian, usually a multiple of 7½° to allow 30-min increments.

Greenwich Mean Time (GMT)

Mean solar time at the Prime Meridian; reference for all world time calculations.

Indian Standard Time (IST)

Time based on 82°30′ E meridian; 5 h 30 min ahead of GMT.

International Date Line (IDL)

Zig-zag 180° meridian where crossing eastward subtracts a day and crossing westward adds a day.

Maximum Longitudinal Spacing

111 km separation of longitudes at the Equator; basis for calculating distance east–west.

Great Circle Characteristics

Intersects Earth’s center, divides the globe into equal halves, and any two great circles bisect each other.