Maps and Web-based Data - Participatory Mapping: New Data, New Cartography - page 70

defend the legitimacy of their application. The validity can
also be questioned in terms of the data rather than the base
map. As the data used are published online, alternative
visualizations can be made so that the map becomes an
ephemeral support that can easily be outdone, which shifts
the validity issue from the map to the data used.

4.2.3.1. Listing the approximations
The limits of these maps have been encapsulated by some
under the term McMaps [DOD 08]. Batty [BAT 10, p.22]
stresses the need to access the base map for an in-depth
analysis; however, this is not possible for the mapping
platform Google Maps, which entails some visual
inconsistencies. Although the Mercator projection, which is
the only one available for Google Maps 19 , gives an accurate
representation for most inhabited regions of the globe,
without too many distortions, the latter are significant at the
poles 20 .

The map “If it were my home” (Table 4.1, map no. 10)
locates, for a given or default area (by geo-location of the IP
address entered by the map user), a surface showing the
extent of flooding in Pakistan in 2010. As the user could
modify the focus of the map by entering a location in the text
bar, the flooding area was subject to distortions from the
Mercator projection. This flaw is considered relatively
significant by the designers of the map as it is mentioned in
the FAQ section that comes with the map. They warn the
website visitors that the reported size of the flooding changes
depending on its position on the globe.

19 Commentary by Bret Taylor, July 2nd 2005. See:

https://groups.google.com/forum/?fromgroups#!msg/Google-Maps-API/g
ZytmchfZB4/5vYheY6xIoIJ.
20 This explains why Alaska appears to be bigger than Brazil on a
Mercator projection, whereas the latter is in reality five times the size of
Alaska: http://fr.wikipedia.org/wiki/Projection_de_Mercator.