Equal area projections conserve area.
Understanding Equal Area Map Projections
Map projections are methods used to represent the three-dimensional surface of the Earth on a two-dimensional plane. This process inevitably involves some form of distortion, as it's impossible to perfectly flatten a sphere without stretching or tearing. Different types of projections minimize different types of distortion.
When the goal is to ensure that the relative sizes of areas on the map are accurate compared to their true size on the Earth, an equal area projection (also known as an equivalent projection) is used. These projections are designed so that any given area on the map maintains the same proportional area as it does on the Earth's surface.
As referenced in cartographic descriptions:
Equal area projections preserve area, at the expense of angles, so the shapes of some places appear skewed. Equidistant projections preserve distances, although only from certain points or along certain lines on the map.
This highlights the fundamental trade-off in map projections: you cannot preserve all properties (area, shape, distance, direction) simultaneously. Equal area projections prioritize preserving area, which means other properties, particularly shape and angles, will be distorted. This often results in landmasses appearing stretched or compressed, especially towards the edges of the map.
Key Features of Equal Area Projections
- Accurate Area Representation: The primary characteristic is that areas on the map are proportional to areas on the ground. This makes them ideal for thematic maps showing distributions like population density or land use.
- Shape Distortion: Shapes are distorted, often significantly. Angles are not preserved.
- Not Conformal: Unlike conformal projections (which preserve angles and shapes locally), equal area projections sacrifice shape for area accuracy.
Examples of Equal Area Projections:
- Albers Equal-Area Conic
- Lambert Equal-Area Azimuthal
- Gall-Peters projection
These projections are valuable tools in fields like geography, environmental science, and urban planning where comparing the true sizes of different regions is crucial.
