Tissot’s Indicatrix: Measuring Distortion in Map Projections

Elizabeth Borneman

Updated:

Tissot’s indicatrix is a mathematical contrivance used in cartography to characterize local distortions in map projections. A major problem in cartography has always been how to accurately depict a three-dimensional object onto a two-dimensional surface.

Maps are Always Distorted

Different map projections have different problems with their individual distortions; distances between objects and the objects themselves are often inaccurate in some way.

Who Created the Tissot’s Indicatrix to Measure Map Distortion?

Tissot’s indicatrix was created by a French mathematician named Nicolas Auguste Tissot between 1859-1871. He showed how the geometry of putting an object like a globe onto a map creates an ellipse that has axes indicating two directions along a scale of maximal and minimal points on a map.

How Distortion is Shown on a Map

The indicatrix not only shows where the map’s distortions are, but how much they are distorted using a scale of magnitude.