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The unicorn of map projections is the one that preserves all the spatial relationships from the globe. Topologically, we know this projection doesn’t exist, as it is impossible to preserve both are...

We created a global database of glacierized volcanoes, using a projection optimized for each volcano, to identify locations where land ice (glaciers and ice sheets) and volcanoes co-exist on Earth. Our spatial database melds the Smithsonian Global Volcanism Database (SGVD) and the Randolph Glacier Inventory 6.0 (RGI). We identified all Holocene volcanoes within the SGVD that have glacier ice within radii of 1 km, 2.5 km, and 5 km, and thus have the potential to impact or be impacted by surrounding ice. Our analysis shows that 245 Holocene volcanoes have glacier ice within the specified radii, which are covered partly or fully by 2584 unique glaciers or the Antarctic Ice Sheet. The volcanoes are located in all major volcano-tectonic settings, although the majority (72%) are in subduction zones built on continental crust (greater than 25 km thick). They also cover the majority of the typical compositional ranges for igneous rocks (basalt to rhyolite). Twenty-nine volcanoes, or 12%, have at least 90% ice cover within 5 km, which together comprise 36% of global glacier area on volcanoes. About 20,000 people live within 5 km of a glacierized volcano, while 160 million people live within 100 km of a glacierized volcano and could be impacted by lahars and/or disruption of their water sources during future eruptions. By merging our database with existing ice thickness model estimates we find 850 ± 290 km3 of ice within 5 km of volcanic vents globally. We compare the eruption history, ice volume, and nearby population estimates to identify the most dangerous volcanoes on Earth. The combination of volcano locations and ice thickness estimates allows us to identify 20 (out of 245) glacierized volcanoes that are most likely to experience ‘thick’ ice eruptions, while the vast majority are more likely to experience ‘thin’ ice eruptions.

For decades, cartographers and cognitive scientists have speculated about the influence of map projections on mental representations of the world. The development of Web 2.0 and web mapping services at the beginning of the 21st century—such as Google Maps, OpenStreetMap, and Baidu Map—led to an enormous spread of cartographic data, which is available to every Internet user. Nevertheless, the cartographic properties of these map services, and, in particular, the selected map projection or the Web Mercator projection, are questionable. The goal of this study is to investigate if the global-scale mental map of young people has been influenced by the increasing availability of web maps and the Web Mercator projection. An application was developed that allowed participants of Belgium and the US to scale the land area of certain countries and continents compared to Europe or the conterminous United States. The results show that the participants’ estimation of the actual land area is quite accurate. Moreover, an indication of the existence of a Mercator effect could not be discovered. To conclude, the young people’s mental map of the world does not appear to be influenced by a specific map projection but by personal characteristics. These elements are varied and require further analysis.

A distance cartogram (DC) is a technique that alters distances between a user-specified origin and the other locations in a map with respect to travel time. With DC, users can weigh the relative travel time costs between the origin and potential destinations at a glance because travel times are projected in a linearly interpolated time space from the origin. Such glance-ability is known to be useful for travelers who are mindful of travel time when finding their travel destinations. When constructing DC, however, uneven urban traffic conditions introduce excessive distortion and challenge user intuition. In addition, there has been little research focusing on DC's user interaction design. To tackle these challenges and realize the potential of DC as an interactive decision-making support tool, we derive a set of useful interactions through two formative studies and devise two novel techniques called Geo-contextual Anchoring Projection and Scalable Road-network Construction. We develop an interactive map system using these techniques and evaluate this system by comparing it against an equidistant map (EM), a widely used conventional layout that preserves the geographical reality. Based on the analysis of user behavior and qualitative feedback, we identify several benefits of using DC itself and of the interaction techniques we derived. We also analyze the specific reasons behind these identified benefits.

We advance an industrial-organization-style measure of the competitiveness of urban public school districts. We find that a majority of the American urban population can choose among at least four school districts. Tiebout choice is a realistic option for most Americans. However, there is substantial variation in the extent of this choice. The most competitive regions are large Urbanized Areas (UAs) in the Northeast and North-Central United States. Smaller UAs are less competitive in this respect. Two regions of the country have much less Tiebout choice: the South and the arid West. Both can be accounted for by scale economies of the past. In the arid West, rural densities were low, which necessitated larger areas to achieve graded schools when one-room school districts started becoming obsolete early in the twentieth century. In the South, segregated schools were a diseconomy of scale that also required larger districts to achieve graded schools for whites and, later on, for blacks. These arguably oversize school districts persist because of the political and legal difficulties in breaking up school districts.