Latitudes and Longitudes - Key Concepts

Locating Places on Earth

• Location is important for knowing the precise place using longitude and latitude.

Latitude

• Angular distance of a point on Earth's surface from the center.

Prime Meridian

• Longitude of zero degrees passing through Greenwich.

Maximum Latitude

• 90 degrees North and South.
• Based on right angle where vertical and horizontal lines cross.

Meridians of Longitude

• Semi-circles running from North Pole to South Pole through the equator.
• Meridian means midday, places along the same meridian experience noon at the same time.

Properties of Lines of Latitude

• Drawn parallel to the Equator, diminishing towards the poles.
• 180 parallels at 1° intervals (90 N, 90 S), Equator at 0° is the only Great Circle.

Properties of Lines of Longitude

• All meridians are Great Circles, dividing Earth into Eastern and Western Hemispheres.
• 360 meridians at 1° intervals.
• Zero degree meridian passes through Greenwich, called Prime Meridian.

Distance Between Parallels of Latitude

• Approximately 111 km.
• $(\frac{40,000 \text{ km}}{360°} = 111 \text{ km})$

Temperate Zones

• North: $23\frac{1}{2}°N$ to $66\frac{1}{2}°N$.
• South: $23\frac{1}{2}°S$ to $66\frac{1}{2}°S$.

Torrid Zone

• Hotter due to direct sun rays.

Frigid Zone

• Colder due to slanting rays and longer winters.

Local Time

• Sun is overhead each meridian after 4 minutes.
• Noon when Sun is overhead, also called Sun time.

Local Time Calculation

• 30°E is 2 hours ahead of Greenwich time (30 x 4 = 120 minutes).

Standard Time

• Necessary to avoid time differences between cities.

Time Zones

• Regions observing uniform standard time.
• India uses 82½°E as Standard Meridian.

Temperature Differences (London vs. Singapore)

• London is at a higher altitude, causing lower temperatures.

International Date Line

• Meridian of 180° in the Pacific Ocean.
• Marks a one-day difference.

Multiple Time Zones

• Countries with vast East to West extension (e.g., USA, Canada, Russia).

Small Circles

• Latitudes other than the Equator.

Great Circles

• Equator is the only Great Circle among parallels of latitude.

Inconvenience of Local Time

• Confusion in schedules due to time differences between cities.

Earth's Grid

• Network of latitudes and longitudes.

Circumference of the Earth

• First measured by Eratosthenes of Egypt.

Climatic Zones

• Torrid/Tropical, Temperate, & Frigid.

Rate of Change of Time

• 4 minutes per longitude.
• $(\frac{360°}{24 \text{ hrs}} = 15° \text{ per hour})$

Locating Position

• Using Earth's grid (latitudes and longitudes).
• Example: Gandhinagar (23.12°N, 72.41°E).

Diagram Interpretation

• PP' represents latitude
• TT' represents the Prime Meridian or 0° longitude.
• Latitude of place X is 40°N

Local Time vs. Standard Time

• Local Time: Varies with longitude. Places on same longitude have same local time.
• Standard Time: Fixed time for places in the same meridian, remains same for a country. Places on the same longitude can have different standard times.

Parallels vs. Meridians

Parallels

• Run West to East.
• Parallel to each other.
• Not of the same length.
• Equator is the only great circle.
• Used for measuring distance.
• Latitude measures up to 180 degrees (90N-0-90S).
• Lines decrease in length.
• Lines of latitude increase in value from equator towards the poles.

Meridians

• Run North to South.
• Not parallel, converge at poles.
• Same length.
• Many great circles.
• Used for measuring local time.
• Longitude measures up to 360 degrees.
• All lines are of equal length.
• Lines of longitude increase in value Eastwards of the Greenwich Meridian.

Equator vs. Prime Meridian

Equator

• 0° latitude.
• Runs East to West.
• Divides the earth into climatic zones.

Prime Meridian

• 0° longitude.
• Runs North to South.
• Divides the earth into time zones.

Latitude Definition

• Angular distance of a point from the Earth's center.