Projection
Overview
Projection is a mathematical transformation that converts geographic coordinates (latitude and longitude) into a flat, two-dimensional representation of the Earth’s surface, allowing for accurate mapping and analysis in a GIS. All projections introduce distortion in area, shape, distance, or direction.
Key Concepts
Developable surface is the geometric shape used for projection (plane, cone, cylinder). Distortion is the unavoidable deformation of geographic properties. Conformal preserves local shape/angles (Mercator). Equal-area preserves area relationships (Albers). Equidistant preserves distances from a point or line. Compromise balances multiple properties (Robinson).
Projection Types
| Type | Preserves | Examples |
|---|---|---|
| Conformal | Shape, angles | Mercator, Lambert Conformal |
| Equal-area | Area | Albers, Mollweide |
| Equidistant | Distance | Azimuthal Equidistant |
| Compromise | Balance | Robinson, Winkel Tripel |
Common Projections
- Web Mercator (EPSG:3857): Web mapping standard
- UTM: Zone-based for regional mapping
- State Plane: High-accuracy US state systems
- Albers Equal-Area: Thematic mapping
Appendix
Created: 2025-12-13 | Modified: 2025-12-13
See Also
- Coordinate Reference System (CRS)
- European Petroleum Survey Group (EPSG)
- Datum
- Geographic Information System (GIS)