Latitude and Longitude

• Latitude and Longitude form a geographical coordinate system describing locations on Earth.

Latitudes

• Latitudes are imaginary horizontal lines extending east to west on the globe.
• Latitudes range from 0° at the Equator to 90° North (North Pole) and 90° South (South Pole).
• Latitudes are also known as Parallels because they never meet and are equidistant.
• Parallels get shorter towards the poles; the Equator is the longest, and a great circle.

Equator

• The Equator is the line with zero degrees latitude.
• The Equator (0° latitude) divides Earth into the Northern and Southern Hemispheres.
• Latitudes play a significant role in determining climate zones.
• There are a total of 181 latitudes, including the Equator.
• 90 latitudes are in the Northern Hemisphere (from 1°N to 90°N).
• 90 latitudes are in the Southern Hemisphere (from 1°S to 90°S).
• 1 latitude accounts for the Equator (0°).
• The total number of latitudes calculation: 90 + 90 + 1 = 181.
• The distance between consecutive latitudes (1° apart) is approximately 111 km (69 miles).

Distance Calculation

• Distance = (π × R/180) × Δθ
• R = 6371 km (Earth's average radius)
• Π = 3.1416
• Δθ = Difference in latitude (in degrees)
• 1° of latitude is approximately 3.1416 × 6371 / 180 ≈ 111 km
• The distance remains nearly constant as latitude lines are parallel.
• Longitude distances vary because meridians converge at the poles.
• The axial tilt of Earth (obliquity) is the angle between Earth's rotational axis and its orbital plane around the Sun.
• The Axial Tilt of the Earth is 23.5°.

Tropic Lines

• The Tropic of Cancer and Tropic of Capricorn are lines of latitude marking the northernmost and southernmost circles where the Sun can be directly overhead at the solstice.
• The Tropic of Cancer is at 23° 26′ 10.5” (23.43624 N).
• The Tropic of Capricorn is at 23° 26'10.5" (23.43624 S).
• The word "tropic" originates from the Greek term "tropos," meaning "turn" or "change."
• The term refers to the sun's perceived change in direction as it reaches these latitudes.
• The Tropic of Cancer marks the northernmost latitude where the sun is directly overhead, occurring at the June solstice (Summer solstice).
• The Tropic of Capricorn marks the southernmost latitude where the sun is directly overhead, occurring at the December solstice (Winter solstice).

Earth's Orbit

• Earth's orbit around the Sun is elliptical, causing variations in the Earth-Sun distance throughout the year.
• The terms come from ancient Greek: "helios" means "Sun," "apo" means "far," and "peri" means "close."
• Aphelion (farthest from the Sun = 152.1 million km) occurs around July 3rd-4th.
• Earth is at its farthest point from the Sun (~152 million km).
• The Sun appears slightly smaller in the sky.
• Perihelion (closest to the Sun = 147.1 million km) occurs around January 3rd.
• Earth is at its closest point to the Sun (~147 million km).
• The Sun appears slightly larger in the sky.
• Earth receives more solar energy during perihelion, but this does not cause summer; seasons are determined by Earth's axial tilt (23.5°), not distance.
• Seasons are NOT caused by Earth's distance from the Sun.
• Seasons are controlled by Earth's axial tilt (23.5°).

Solstices

• Summer Solstice (June Solstice): The Sun is overhead at the Tropic of Cancer (23.5°N).
• The Northern Hemisphere experiences the longest day and shortest night.
• The Northern Hemisphere gets the maximum daylight hours.
• The Arctic Circle (66.5°N) experiences 24 hours of daylight.
• Occurs around June 21st each year.
• During the Summer Solistice, the Southern Hemisphere experiences the shortest day and longest night. The Antarctic Circle (66.5°S) experiences 24 hours of darkness (Polar Night).
• Winter Solstice (December Solstice): The Sun is overhead at the Tropic of Capricorn (23.5°S).
• The Southern Hemisphere experiences the longest day and shortest night.
• The Southern Hemisphere experiences maximum daylight hours.
• The Antarctic Circle (66.5°N) experiences 24 hours of daylight.
• Occurs around December 21st each year.
• During the Winter Solistice, the Northern Hemisphere experiences the shortest day and longest night. The Arctic Circle (66.5°S) experiences 24 hours of darkness (Polar Night).

Equinox

• The Sun is directly overhead at the Equator during an equinox.
• Day and night are nearly equal in length all over the Earth during equinoxes.
• Equinoxes occur twice a year.
• Spring equinox occurs on March 20th - 21st.
• Fall equinox occurs on September 22nd-23rd.

Longitude

• Longitudes (Meridians) are imaginary vertical lines (semicircles) extending from the North Pole to the South Pole on the globe.
• The Prime Meridian is the line with zero degrees longitude.
• Longitudes range from 0° at Greenwich, London, to 360° at the midway point of the Pacific Ocean.
• The 180° longitude line / meridian is called the International Date Line (IDL) and is directly opposite the 0° meridian.
• Meridians are instrumental in determining time zones and local time.
• There are 360 meridians.
• The distance between meridians is not equal.
• At the Equator: 1° = 111 km
• At 30°N and 30°S: 1° = 96.5 km
• The distance decreases until it reaches zero at the poles.

International Date Line

• The International Date Line was established in 1884 and passes through the Mid-Pacific Ocean, roughly following the 180° line.
• Traveling East to West (e.g., Japan to the United States) results in Gaining a day and adding a day
• If it is Monday in Japan, traveling westward to the United States results in it becoming Sunday.
• Traveling West to East (e.g., United States to Japan) results losing a day
• If it is Monday in the United States, traveling eastward to Japan results in it becoming Tuesday.
• Earth's actual rotation time is 23 hours, 56 minutes, and 4 seconds, not exactly 24 hours.

Coordinate System

• Coordinate systems are commonly described in two units: Degree Minute Seconds (DMS).
• Coordinates of Faisalabad Clock Tower:
• Latitude: 31° 25′ 07.22"N
• Longitude: 73° 04′ 44.90″E
• Converting Degree Minute Seconds (DMS) to Decimals for Latitude:
• 31° 25′ 07.22"N
• 31 + 25/60 + 7.22/3600
• 31 + 0.4166 + 0.00200 = 31.418
• Converting Degree Minute Seconds (DMS) to Decimals for Longitude:
• 73° 04′ 44.90″E
• 73 + 04/60 + 44.90/3600
• 73 + 0.0666 + 0.01247 = 73.079
• Convert Decimals to Degree Minute Seconds (DMS):
• 31.4187
• 31.4187 x 60 = 31 25.122
• 31 25.122 x 60 = 31 25 7.32
• 31° 25′ 7.22"
• Coordinates:
• Latitude: 24° N - 37° N
• Longitude: 61° E - 77° E
• Total Area: 881,913 sq km
• Altitude:
• Highest point: K-2 (8611m)
• Deepest point: Dasu patan (6500m)
• Lowest point: Sea level 0 (feet)