Areal Interpolation

Areal interpolation is the family of methods for transferring attribute data — populations, counts, rates — from one set of areal units (the source zones) onto a different, incompatible set (the target zones). The need arises constantly in geography because census tracts, postal zones, electoral districts, and grid cells rarely align, yet analysts must combine data reported on mismatched geographies. The methods range from simple area-proportional weighting through ancillary-informed dasymetric refinement to Waldo Tobler's 1979 volume-preserving pycnophylactic smoothing, each trading simplicity for accuracy.