Map Projection Fundamentals

Map Projection Fundamentals

• Map Projection: A method to represent the curved surface of the Earth onto a flat surface.

• Graticule: A network of parallels (lines of latitude) and meridians (lines of longitude) displayed on a map, representing the Earth's grid system.

• Generating Globe: A model of the Earth used as a reference for creating projections. It's often a wire or glass globe.

• Developable Surface: A geometric shape onto which the Earth's surface is projected. Common surfaces include cones and cylinders.

• Cone Projection Examples:

  • Conical Projection with one standard parallel
  • Conical Projection with two standard parallels
  • Bonne's Projection
  • Polyconic Projection

• Cylindrical Projection Examples:

  • Cylindrical Equal Area Projection
  • Cylindrical Equi-Distant Projection
  • Mercator's Projection

• Standard Parallel: The parallel of latitude where the developable surface touches the generating globe. The scale is most accurate along this parallel.

• Central Meridian: The central meridian on which the radial scale (scaling in a straight line outward from the central meridian) is accurate. Distortion increases further from the central meridian.

• Constant of Cone: This value relates the angle at the vertex of a cone to the angle of the pole on the generating globe, and it helps define the conical projection. The formula is: Constant of Cone (n) = α/360, where α is the angle of the cone's vertex.

• Scale Factor: The ratio between the map's scale and the real-world scale, or the ratio of a distance on the map to the actual distance on the ground.

Types of Scale Factors

• Tangential Scale Factor (TSF): Compares the length of a parallel of latitude on the globe to the length of the same parallel on the map.

• Radial Scale Factor (RSF): Compares the length of a meridian on the globe to the length of the same meridian on the map.

Datum & Geoid

• Datum: A reference surface that defines the position of points on the Earth. The most common datum is the World Geodetic System 1984 (WGS-84), which is based on the mean sea level.

• Geoid: The actual shape of the Earth, which is an irregular, slightly flattened sphere.

Orthodrome & Loxodrome (Great Circle & Rhumb Line)

• Great Circle (Orthodrome): The shortest distance between two points on the surface of the Earth. On a great circle, the compass bearing changes constantly.

• Rhumb Line (Loxodrome): A line that intersects all meridians at a constant angle. On a rhumb line, the compass bearing remains the same. Loxodromes appear as straight lines on Mercator's Projection.

Explore the fundamentals of map projections, including concepts such as graticule, developable surfaces, and examples of both cone and cylindrical projections. This quiz covers the various methods used to represent the Earth's surface on a flat map and the significance of standard parallels in projection techniques.