Web Maps for Global Data Visualization:
Does Mercator Matter?

Sam Lumley, Renee Sieber

Web maps:

Are easy to make and use

Mashup data

Look cool

Help make meaning from data

Mercator is everywhere

Why Mercator?

Does Mercator matter?

Present study

120 MTurk Participants

Two groups:

We asked:

How much of the earth's surface is covered by each colour?

Which pollutant is most threatening?

Results: area estimation

Results: Qualitative

Is pollutant A (red) more threatening that pollutant E (blue)?

Control: 17%

Mercator: 50%

Results: The Mercator Challenge

Are experts any better?

Conclusions Does Mercator matter?

Obviously, yes

Visual design matters

What should we do instead?

Use static

Wait for Google/ Mapbox to sort their shit out

Adaptive composite maps

Thank you!

Slides available at:


Links below each slide