Projection
The mathematical transformation of the earth’s curved surface onto a flat map, essential for accurate spatial analysis and measurement (inferred from standard GIS usage).
Explain Projection?
In the context of GIS (Geographic Information Systems), projection is the mathematical process that is used to depict the Earth's curving, three-dimensional surface on a two-dimensional, flat map. Due to the Earth's ellipsoidal or spherical shape, any depiction of its surface on a flat surface will invariably introduce some kind of distortion, whether it be in direction, distance, size, or shape.
Essential Ideas in Projection:
Purpose: Projections allow geographic coordinates (latitude and longitude) to be converted into a plane coordinate system (e.g., x, y) so that maps and spatial analyses can be performed accurately on a flat surface.
Types of Projections: Projections are designed to preserve one or more spatial properties:
Conformal: Preserves shape (e.g., Mercator projection)
Equal-Area: Preserves area (e.g., Albers Equal Area)
Equidistant: Preserves distances from certain points or lines
Azimuthal: Preserves direction from a central point
Projection Surfaces: The Earth is typically projected onto one of three geometric surfaces:
Cylindrical (e.g., Mercator)
Conic (e.g., Lambert Conformal Conic)
Planar or Azimuthal (e.g., Polar Stereographic)
Coordinate Systems: The projection results in a projected coordinate system, which defines how the flat coordinates (e.g., meters or feet) relate to the curved Earth.
Related Keywords
The curved surface of the Earth is somewhat distorted when it is projected onto a flat map. Azimuthal (correct from a central point), conic (fits mid-latitudes), and cylindrical (preserves direction) are common forms. The purpose of the map determines the selection.
While a projection converts the curving Earth onto a flat map, allowing for precise mapping and analysis, a coordinate system uses numbers such as latitude and longitude to designate locations on Earth.
A popular coordinate system in GIS, the Universal Transverse Mercator (UTM) projection splits the Earth into 60 zones, each 6° broad by longitude. For mapping small to medium areas, it offers a highly precise rectangular grid that minimizes distortion in area, shape, and distance inside each zone. Because UTM describes locations in meters, making computations simple, it is perfect for engineering tasks, navigation, and extensive geographical analysis.
In mapping, projection transformation is the process of turning the Earth's curving surface—a 3D ellipsoid or sphere—into a flat 2D map. Different map projections are employed depending on the purpose—some keep shape, while others conserve area, distance, or direction—because it is impossible to flatten the Earth without distortion. For geographic characteristics to be appropriately represented on maps in cartography and GIS, this transformation is necessary.