Choropleth map

Abstract: The purpose of this exercise is to help students review some important aspects of choropleth maps that appear in a selected geographic journal for a specific time period. Through this exercise, students in a cartography course can identify the most common number of classes used for choropleth maps, the most popular method used to determine the class intervals, the most frequently used legend structure, and the most popular symbol used in choropleth maps. This exercise will provide an opportunity for the student to judge the published maps against accepted cartographic standards. The exercise can be used either as an alternative to or independently of the atlas review.

Abstract: The line-up task hides a plot of real data amongst a line-up of decoys built around some plausible null hypothesis. It has been proposed as a mechanism for lending greater reliability and confidence to statistical inferences made from data graphics. The proposition is a seductive one, but whether or not line-ups guarantee consistent interpretation of statistical structure is an open question, especially when applied to representations of geo-spatial data. We build on empirical work around the extent to which statistical structure can be reliably judged in map line-ups, paying particular attention to the strategies employed when making line-up judgements. We conducted in-depth experiments with 19 graduate students equipped with a moderate background in geovisualization. The experiments consisted of a series of map line-up tasks with two map designs: choropleth maps and a centroid-dot alternative. We chose challenging tasks in the hope of exposing participants’ sensemaking activities. Through structured qualitative analysis of think-aloud protocols, we identify six sensemaking strategies and evaluate their effects in making judgements from map line-ups. We find five sensemaking strategies applicable to most visualization types, but one that seems particular to map line-up designs. We could not identify one single successful strategy, but users adopt a mix of different strategies, depending on the circumstances. We also found that choropleth maps were easier to use than centroid-dot maps.

Abstract: COVID-19 is an acute respiratory disease that was classified as a pandemic on March 11th, 2020, by the World Health Organization. Many efforts have been made in order to monitor and present the spatial distribution of cases of this disease and at various scales. It is possible to observe many different methodological approaches, such as choropleth maps and cartograms, proportional symbol maps, dynamics or statics, as well as graphs and tables. Each resource adapted to the specificities of the scale or regional context. In order to present methodological contributions for the representation of epidemiological data, we present the spatial distribution of confirmed cases of COVID-19 in Minas Gerais until the date of June 21st, 2020, using Univariate Contiguous Areas Cartograms, a Bivariate Choropleth Map and a Proportional Symbol Map for the representation of relative and absolute data. The results showed the tendency of municipalities with larger populations or higher demographic densities to present more confirmed cases of the disease and the measures that relativize the absolute numbers of confirmed cases with the resident population, when represented by cartograms or by the Bivariate Choropleth map, revealed information which used to be visually hidden by the differences of the areas of the municipalities.