Users of the Ushahidi website were prompted to report acts of violence in Kenya. Following the election in 2008, many Kenyans believed the new president manipulated votes in his favor, which led to violence throughout the country. The Ushahidi (signifying “testimony” in Swahili) website developed an online crowd sourcing map application. This interactive map application allows map users to explore and find new patterns across space and time.Īside from altering color to represent different categories on a map, changing the shape of a point symbol can help map users differentiate different groups.
Every crime location is displayed as a circular point, where each crime category is differentiated through hue (arson: orange, homicide: purple, sexual abuse: blue). The CrimeViz map application ( CrimeViz) developed in the GeoVISTA Center at Penn State visualizes violent crimes reported from the District of Columbia Data Catalog ( DC Data Catalog). In mapping categorical data, cartographers often focus on displaying the different categories or classes through shape or color hue. For example, the category of a beach could not be described as two times the value of a wetland it is different in kind rather than amount. 3.2.1 Mapping Categorical DataĪs mentioned in the section on color schemes, categorical data are data that can be assigned to distinct non-numerical categories. A primary distinction here is between maps that depict categorical (qualitative) data and those that depict numerical (quantitative) data. In the rest of this chapter, we will explore different types of thematic maps and consider which type of map is conventionally used for different types of data and different use goals. Alternatively, thematic maps can have a decision-making purpose (e.g., to help users make travel decisions as with the real-time traffic map). demographics as with the population change map). Often, that purpose has to do with revealing the spatial distribution of one or two attribute data sets (e.g., to help readers understand changing U.S. As introduced above, unlike reference maps, thematic maps are usually made with a single purpose in mind.
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