Bivariate Map

A bivariate map is an advanced cartographic technique that encodes two quantitative variables on a single map, most often through a grid of blended colors. Each variable is classified independently, and the resulting combinations form a matrix legend—commonly three-by-three or four-by-four—where each cell represents a unique pairing of low-to-high values for both variables. Bivariate maps are powerful for exploring spatial correlations. For example, overlaying income level and educational attainment on a census tractCensus TractA Census Tract is a small, relatively stable statistical subdivision of a county designed for demographic analysis. C... map immediately highlights areas where both are high, both are low, or one dominates the other. This type of insight requires two separate maps when using traditional univariate techniques, making comparison far more difficult. Designing effective bivariate maps demands careful color selection. Cartographers typically choose two base hues that blend predictably, such as blue and red producing purple in the overlap. The legend must be clearly presented so readers can decode both variables. Joshua Stevens and other cartographic researchers have published well-tested bivariate palettes. Tools for creating bivariate maps include QGISQGISQGIS is a user-friendly, open-source GIS platform that provides tools for geospatial data analysis, mapping, and inte... with bivariate plugins, D3.js, and R packages like biscale, and they are increasingly supported in modern web mapping libraries.