  Area cartograms are map-based data visualizations in which the area of each
map region is proportional to the data value it represents. Long utilized in
print media, area cartograms have also become increasingly popular online,
often accompanying news articles and blog posts. Despite their popularity,
there is a dearth of cartogram generation tools accessible to non-technical
users unfamiliar with Geographic Information Systems software. Few tools
support the generation of contiguous cartograms (i.e., area cartograms that
faithfully represent the spatial adjacency of neighboring regions). We thus
reviewed existing contiguous cartogram software and compared two web-based
cartogram tools: fBlog and go-cart.io. We experimentally evaluated their
usability through a user study comprising cartogram generation and analysis
tasks. The System Usability Scale was adopted to quantify how participants
perceived the usability of both tools. We also collected written feedback from
participants to determine the main challenges faced while using the software.
Participants generally rated go-cart.io as being more usable than fBlog.
Compared to fBlog, go-cart.io offers a greater variety of built-in maps and
allows importing data values by file upload. Still, our results suggest that
even go-cart.io suffers from poor usability because the graphical user
interface is complex and data can only be imported as a comma-separated-values
file. We also propose changes to go-cart.io and make general recommendations
for web-based cartogram tools to address these concerns.
