Shapes on a plane: Evaluating the impact of projection distortion on spatial binning

Cartography and Geographic Information Science
By: , and 



One method for working with large, dense sets of spatial point data is to aggregate the measure of the data into polygonal containers, such as political boundaries, or into regular spatial bins such as triangles, squares, or hexagons. When mapping these aggregations, the map projection must inevitably distort relationships. This distortion can impact the reader’s ability to compare count and density measures across the map. Spatial binning, particularly via hexagons, is becoming a popular technique for displaying aggregate measures of point data sets. Increasingly, we see questionable use of the technique without attendant discussion of its hazards. In this work, we discuss when and why spatial binning works and how mapmakers can better understand the limitations caused by distortion from projecting to the plane. We introduce equations for evaluating distortion’s impact on one common projection (Web Mercator) and discuss how the methods used generalize to other projections. While we focus on hexagonal binning, these same considerations affect spatial bins of any shape, and more generally, any analysis of geographic data performed in planar space.

Publication type Article
Publication Subtype Journal Article
Title Shapes on a plane: Evaluating the impact of projection distortion on spatial binning
Series title Cartography and Geographic Information Science
DOI 10.1080/15230406.2016.1180263
Volume 44
Year Published 2017
Language English
Publisher Taylor and Francis
Contributing office(s) Center for Geospatial Information Science (CEGIS)
Description 12 p.
First page 410
Last page 421
Online Only (Y/N) N
Additional Online Files (Y/N) N
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