Web Maps for Spatial Data Visualisation–Does Mercator Matter?

Authors: Sam Lumley*, McGill University
Topics: Cartography, Geographic Information Science and Systems, Communication
Keywords: cartography, data interpretation, experimental psychology, geovisualisation, geoweb, projection, scientific communication, spatial cognition ,web maps
Session Type: Poster
Day: 4/11/2018
Start / End Time: 10:00 AM / 11:40 AM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: Download


Web maps are a popular choice for geospatial data visualisation, providing a platform for interactive data navigation and information sharing. In web mapping applications, the Web Mercator projection has become a standard, despite long having been considered inappropriate for scientific data representation due to its area distortion of higher latitude regions. The presented research applied experimental geovisualisation methods to assess the implications of Web Mercator’s area distortion effects for public data interpretation. Specifically, we look to whether people identify projection distortions, and if they do, whether they are able to account for them in subsequent data interpretation. We recruited one hundred and twenty participants via Amazon’s online recruitment platform Mechanical Turk to complete an online survey, in which participants were asked to make area estimates of five coloured regions represented on a global map. We employed a between-subjects experimental design with two conditions corresponding to the maps viewed by participants–a quasi-control group using a cylindrical equal-area projection and a treatment group using a Web Mercator projection. In general, participants failed to discount for the projection distortions and interpreted the two maps differently as a result. These findings were further corroborated by participants’ responses to questions about map preference and suitability. Our results provide an empirical basis for claims about the distortion effects of the Mercator projection, further implicating its appropriateness for the display of global scientific data in web maps.

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