Map Projections

Map Projections

• A way to represent the curved surface of the Earth on a 2D map
• Methods to preserve:
  • Shape: conformal projections (e.g. Mercator)
  • Size: equal-area projections (e.g. Gall-Peters)
  • Distance: equidistant projections
  • Direction: azimuthal projections
• Common map projections:
  • Mercator: preserves shape, but distorts size and distance at high latitudes
  • Gall-Peters: preserves size, but distorts shape
  • Azimuthal: preserves direction, but distorts shape and size

Geographic Coordinates

• System to locate points on the Earth's surface using latitude and longitude
• Latitude:
  • Measures distance from the Equator (0° to 90° N or S)
  • Also known as parallels
  • Lines that run east-west
• Longitude:
  • Measures distance from the Prime Meridian (0° to 180° E or W)
  • Also known as meridians
  • Lines that run north-south
• Coordinates are written in the format: latitude, longitude (e.g. 37.7749° N, 122.4194° W)
• Latitude and longitude can be measured in degrees, minutes, and seconds (e.g. 37° 46' 30" N, 122° 25' 10" W)

Map Projections

• Map projections are methods to represent the curved Earth's surface on a 2D map
• Four key properties to preserve in map projections:
  • Shape
  • Size
  • Distance
  • Direction
• Conformal projections preserve shape, but can distort size and distance
• Equal-area projections preserve size, but can distort shape
• Equidistant projections preserve distance, but can distort shape and size
• Azimuthal projections preserve direction, but can distort shape and size

Common Map Projections

• Mercator projection:
  • Preserves shape
  • Distorts size and distance at high latitudes
  • Used for navigation, as it preserves shape and direction
• Gall-Peters projection:
  • Preserves size
  • Distorts shape
  • Used for educational and cultural purposes, as it presents a more accurate representation of the Earth's surface
• Azimuthal projection:
  • Preserves direction
  • Distorts shape and size
  • Used for mapping small areas, such as cities or neighborhoods

Geographic Coordinates

• Geographic coordinates are a system to locate points on the Earth's surface using latitude and longitude
• Latitude:
  • Measures distance from the Equator (0° to 90° N or S)
  • Also known as parallels
  • Runs east-west
• Longitude:
  • Measures distance from the Prime Meridian (0° to 180° E or W)
  • Also known as meridians
  • Runs north-south
• Coordinates are written in the format: latitude, longitude (e.g. 37.7749° N, 122.4194° W)
• Coordinates can be measured in degrees, minutes, and seconds (e.g. 37° 46' 30" N, 122° 25' 10" W)

Geographic Coordinates

• Geographic coordinates are a way to locate a point on the Earth's surface using longitude and latitude.

Latitude (φ)

• Measures distance north or south of the Equator (0° latitude).
• Ranges from 0° at the Equator to 90° at the North or South Pole.
• Latitude is divided into degrees, minutes, and seconds (e.g., 40° 26' 46" N).
• 1 degree of latitude is equal to approximately 111 kilometers (69 miles).

Longitude (λ)

• Measures distance east or west of the Prime Meridian (0° longitude).
• Ranges from 0° at the Prime Meridian to 180° east or west.
• Longitude is divided into degrees, minutes, and seconds (e.g., 74° 0' 23" W).
• 1 degree of longitude is equal to approximately 111 kilometers (69 miles) at the Equator.

Key Concepts

• Geographic coordinate system is a system that uses latitude and longitude to locate points on the Earth's surface.
• The Prime Meridian is an imaginary line that passes through Greenwich, England, and is designated as 0° longitude.
• The Equator is an imaginary line that runs around the middle of the Earth, dividing it into the Northern and Southern Hemispheres, and is designated as 0° latitude.

Learn about ways to represent the Earth's curved surface on a 2D map, including conformal, equal-area, equidistant, and azimuthal projections. Compare common map projections like Mercator and Gall-Peters.