[metrics-bugs] #24563 [Metrics/Atlas]: Relay Search map has severe area distortions

Tor Bug Tracker & Wiki blackhole at torproject.org
Fri Dec 8 13:48:26 UTC 2017

#24563: Relay Search map has severe area distortions
     Reporter:  teor           |      Owner:  metrics-team
         Type:  defect         |     Status:  new
     Priority:  Medium         |  Milestone:
    Component:  Metrics/Atlas  |    Version:
     Severity:  Normal         |   Keywords:
Actual Points:                 |  Parent ID:
       Points:                 |   Reviewer:
      Sponsor:                 |
 I'm concerned that the Relay Search map represents countries and
 continents poorly.

 It uses the d3.geo.mercator() projection, which is not recommended for
 comparison maps like ours:
 The spherical Mercator projection...introduces severe area distortion at
 world scale and thus is not recommended for choropleths.

 One obvious issue is that India and the EU are about the same size, but
 the EU looks larger. Similarly, Greenland is smaller than India, but looks
 much larger. Here's a list of countries in order of area:

 I suggest we use an equal-area projection instead. It's much better suited
 to the kinds of comparisons that we're doing.

 None of the built-in projections are rectangular equal-area:

 Extra projections are available here:

 This is the only rectangular equal-area projection without significant

 Here's the line in js/views/aggregate/map.js we'll need to change, as well
 as adding the d3-geo-projection import:
 var projection = d3.geo.mercator()

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24563>
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