A cartographic representation that maintains the relative sizes of geographic features is termed an equivalent, or authalic, projection. It ensures that areas on the map are proportional to their corresponding areas on Earth. This characteristic is achieved at the expense of distorting other properties, such as shape, angle, or scale. A common example is the Albers equal-area conic projection, frequently used to map regions with an east-west orientation, like the contiguous United States, as it minimizes area distortion while maintaining reasonable shape accuracy.
Maintaining areal fidelity is crucial for applications where accurate comparisons of region size are paramount. This includes studies of population density, land use, resource distribution, and environmental change. By accurately representing the relative sizes of areas, these projections minimize bias in spatial analysis and facilitate more reliable interpretations. Historically, the development of these mapping techniques addressed the need for quantitative assessments of geographical phenomena, shifting focus from purely qualitative descriptions to more precise measurements.
