# Module 6. Geovisualization ## Learning Objectives * Differentiate cartography and geovisualization. * Identify a visual variable and give an example of how it might be used to show variation in data on a map. * Use proper map components in the design of a map. * Assess the qualities of a map and determine its purpose and audience. ## Lecture Slides {% embed url="" %} Lecture 6. Geovisualization {% endembed %} ## Assignments * [ ] Lab Assignment * [ ] Quiz 6 * [ ] Lecture Video ## Overview **Cartography** is the science and art of map-making. You may encounter the term **geovisulization**, the process of creating interactive visualizations of geographic data. While both cartography and geovisualization involve the use of spatial data, cartography is more focused on creating static maps, while geovisualization is more focused on creating dynamic, interactive visualizations. ## Map Components A **map** is a visual representation of the features of an area or region, typically drawn to a specific scale and using a set of symbols and conventions to represent geographic features. A map is * Title - descriptive of the location and purpose/theme * North Arrow - provides orientation * Legend - visual explanation of the map symbology * Scale - describes the relationship between map distance and ground distance * Grid Reference - network of columns and rows independent of the maps CRS that provides location information. * Metadata - explanation about the data source, map projection, accuracy, and production date

Figure 1. Map Components

## Types of Maps There are two main categories of maps. **Reference maps** show political features, physical features, topographic features, or some combination of these elements for a region of the Earth's surface. In contrast, **thematic maps** show the geographic pattern of a specific topic or theme in a geographic region. ### Reference Maps Figure 6.1 displays a USGS topographic map. These maps are a great example of the reference map type. A typical topographic map depicts detailed information about the physical surface, including contour lines for elevation changes and water features. In addition to physical features, cultural features such as transportation, urban boundaries, and infrastructure are symbolized on these maps.
USGS Topographic Map

Fgure 6.1 1969 1:24,000 USGS Topographic Map, Bondville, Illinois

### Thematic Maps There are many types of thematic maps. There are six types of thematic maps. They are differentiated by the symbology that they use. * Choropleth Maps * Dot Density Maps * Isopleth/Isarithmic Maps * Dasymetric Maps * Proportional or Graduated Symbol Maps * Flow Maps Thematic maps are classified based on the visual variable that they use to show variation in the spatial data they display. **Visual variables** are visual qualities that can be varied to show differences in data values. First proposed in relation to cartography by French cartographer Jacque Bertin in 1967. These visual variables are * Position * Color hue * Color value * Size * Shape * Orientation * Texture Some visual variables are helpful for displaying quantitative data (e.g., color hue, color value, size), and other visual variables are useful for qualitative data (e.g., color hue, shape, texture). We can exploit this information in our design to clarify our message. #### Choropleth Maps A **choropleth map** uses variations in color to represent variations in data. For quantitative data, variation in color value can be used to show variation in the data, and for qualitative data, variation in color and hue can show different categorical classes. ## Visual Communication The ultimate goal of a map is to communicate a message. **Visual communication** is a process of using visual elements to transfer information. Maps are one form of visual communication; others include pictures, posters, graphs, and charts. To design a map, you should ask yourself three questions. First, *who will be your map user?* Understanding your map user will help you to select the appropriate data and the way that the data is presented. For example, a park manager has different information needs than a forest ecologist. In addition to these domain differences, the level of knowledge is another key aspect of your user that you should consider. For example, a middle school student's understanding of the city is much different than an adult's. Finally, accessibility is a key requirement of all maps. Does your map user have visual impairments that might impact the way that they see your map? By being thorough in your understanding of your map user, you can design a map that best suits their needs. Second, *how is the map to be served to your user*? First, consider if your map is to be displayed using a static material, like paper or technology-enabled devices. Technology-enabled maps often require some level of user interaction. Just think about your use of Google Maps or Bing Maps for navigation. These types of dynamic maps require interaction design in addition to visual design. Finally, different types of technology have different types of displays. Both screen size and resolution are important factors when designing your map. For example, if your computer monitor has the dimensions of 1366 x 768 pixels and a resolution of 100.45 pixels per inch (PPI) while your smartphone has the dimensions of 2560 x 1440 pixels and a 575.92 PPI, your image will have a much harsher appearance on the smartphone screen. There are many tools available that you can use to test out your design in various formats. Third, *what is the purpose of your map*? While we discussed the general differences between reference maps and thematic maps above, there are many different types of maps even within those categories. For example, reference maps, such as transportation maps, are commonly used for navigational purposes. In the other case, thematic maps called flow maps can be used to show trends in shipping traffic. While both of these maps consider aspects of transportation, their purposes are very different and require different data and design approaches. ## Readings * Golebiowska, I., Korycka-Skorupa, J., and Slomska-Przech, K. (2021). Common Thematic Map Types. *The Geographic Information Science & Technology Body of Knowledge* (2nd Quarter 2021 Edition), John P. Wilson (ed.). DOI: [10.22224/gistbok/2021.2.7(link is external)](https://doi.org/10.22224/gistbok/2021.2.7). * White, T. (2017). Symbolization and the Visual Variables. The Geographic Information Science & Technology Body of Knowledge (2nd Quarter 2017 Edition), John P. Wilson (ed.). DOI: [10.22224/gistbok/2017.2.3](https://gistbok.ucgis.org/bok-topics/symbolization-and-visual-variables)