Latitude and Longitude

• Latitude and Longitude form a geographical coordinate system to describe a location on Earth

Latitudes

• Latitudes are imaginary horizontal lines extending from East to West
• Latitudes range from 0° at the Equator to 90° North (North Pole) and 90° South (South Pole)
• Lines of latitude are also known as parallels
• Parallels never intersect and remain equidistant from each other
• Latitude lines shorten towards the poles, the Equator being the longest, forming a great circle

Equator

• A line of zero-degree latitude is called the Equator
• The Equator (0° latitude) divides Earth into the Northern and Southern Hemispheres
• Latitudes significantly determine climate zones
• There are 181 total 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)
• And 1 latitude for the Equator (0°)
• The distance between two consecutive latitudes (1° apart) is approximately 111 km (69 miles)

How to Calculate Latitude Distance

• The formula to calculate distance is: Distance = (π × R/180) × Δθ
• R (Earth's average radius) = 6371 km
• Π = 3.1416
• Δθ = Difference in latitude (in degrees)
• Example: For 1° latitude: 3.1416 × 6371 / 180 ≈ 111 km
• The distance remains nearly constant because latitude lines are parallel
• Longitude distances vary since meridians converge at the poles

Axial Tilt

• The axial tilt of Earth (obliquity) is the angle between Earth's rotational axis and its orbital plane around the Sun
• Earth's axial tilt measures 23.5°

Tropic of Cancer and Capricorn

• The Tropic of Cancer and Capricorn are lines of latitude which mark 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), and the Tropic of Capricorn is at 23° 26′ 10.5” (23.43624 S)
• The term "tropic" originates from the Greek word "tropos," signifying "turn" or "change"
• This refers to the Sun's apparent "turn back" when reaching these latitudes
• The Tropic of Cancer is the northernmost latitude where the sun is directly overhead
• This occurs during the June solstice (Summer solstice)
• The Tropic of Capricorn is the southernmost latitude where the sun is directly overhead
• Which occurs on the December solstice (Winter solstice)

Earth's Orbit

• Earth's orbit around the Sun is elliptical, causing the distance between them to vary throughout the year
• The terms come from ancient Greek: "helios" means "Sun," "apo" means "far," and "peri" means "close"
• Aphelion is the farthest point 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
• Perihelion is the closest point 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
• More solar energy reaches Earth, but it does NOT cause summer because seasons are controlled by Earth's axial tilt (23.5°), not distance

Seasons

• Seasons are NOT caused by Earth's distance from the Sun
• Seasons are controlled by Earth's axial tilt (23.5°)

Summer Solstice (June Solstice)

• The Sun is directly overhead at the Tropic of Cancer (23.5°N)
• The longest day and shortest night of the year occur in the Northern Hemisphere, resulting in maximum daylight hours
• The Arctic Circle (66.5°N) experiences 24 hours of daylight
• Occurs around June 21st
• Conversely, the Southern Hemisphere experiences the shortest day and longest night, with the Antarctic Circle (66.5°S) experiencing 24 hours of darkness (Polar Night)

Winter Solstice (December Solstice)

• The Sun is directly overhead at the Tropic of Capricorn (23.5°S)
• The longest day and shortest night of the year occur in the Southern Hemisphere, resulting in maximum daylight hours
• The Antarctic Circle (66.5°S) experiences 24 hours of daylight
• Occurs around December 21st
• Conversely, 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
• Day and night are nearly equal in length all over the Earth
• Occurs twice a year
• Spring equinox: Occurs March 20th - 21st
• Fall equinox: Occurs September 22nd - 23rd

Longitude (Meridians)

• Longitudes are imaginary vertical lines (semicircles) drawn/extended/run on the globe from the North to South Pole
• Longitudes are also called meridians

Prime Meridian

• The line with zero-degree longitude is called the Prime Meridian
• Longitudes range from 0° at Greenwich, London, to 360° at the midway of the Pacific Ocean
• The 180° longitude line/meridian is called the International Date Line (IDL), directly opposite the 0° meridian
• They determine time zones and local time
• There are 360° total meridians
• The distance between any two meridians is not equal
• At the Equator, 1° = 111 km
• At 30°N and 30°S, 1° = 96.5 km
• Decreases to zero at the poles

International Date Line

• Established in 1884, it passes through the Mid-Pacific Ocean, roughly following the 180-degree line
• Travel East to West (e.g., Japan to United States) results in adding a day (gain a day)
• If it is Monday in Japan and travel westward to the United States, it becomes Sunday
• Travel West to East (e.g., United States to Japan) results in losing a day
• If it is Monday in the United States and travel eastward to Japan, it becomes Tuesday
• Earth doesn't take 24 hours to rotate on its axis
• It actually takes 23 hours, 56 minutes, and 4 seconds

Coordinate Systems

• Coordinate systems commonly describe locations 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 DMS to Decimals

• Example Latitude: 31° 25′ 07.22"N
  • 31 + 25/60 + 7.22/3600
  • 31 + 0.4166 + 0.00200 = 31.418
• Example Longitude: 73° 04′ 44.90″E
  • 73 + 04/60 + 44.90/3600
  • 73 + 0.0666 + 0.01247 = 73.079

Converting Decimals to DMS

• Example: 31.4187
  • 31. 4187 x 60 = 31 25.122
  • 32. 25. 122 x 60 = 31 25 7.32
  • Final answer: 31° 25′ 7.22"

Additional 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)