Basemaps: Leveraging Location

Basemaps: Leveraging Location 

Basemaps are essential – they provide the context for your map data. Selecting a basemap should never be just an afterthought, and though the final choice is always subjective, you can make a better decision by considering your map purpose, audience, and the nature of your overlay data.

Street Maps

Often the default basemap used in business web-mapping applications. Helpful when highly-detailed locational context is necessary (particularly for navigation). Though pre-designed street basemaps may not have the ideal aesthetic for overlaying complex data, they are particularly useful at large scales (at which they appear less visually cluttered) or when overlaying relatively simple social data (e.g., for a map showing all locations of a restaurant chain).

Figure 1.5.1 The OpenStreetMap basemap

Credit: OpenStreetMap © OpenStreetMap contributors. The data is available under the Open Database License (CC BY-SA).

Satellite Imagery

Often useful for environmental or engineering applications. May be useful in rural areas that cannot be well-understood using street maps (as few streets exist). The colors and detail make overlay data much more challenging to design than over subtle basemaps – satellite basemaps work best when GIS data is structured and simple and understanding the physical structure of the landscape is essential to the mapping function (e.g., for a map of local water pipelines).

Figure 1.5.2 An imagery basemap

Credit: Screen capture from ArcGIS Pro

Greyscale Basemaps

Usually reserved for thematic mapping, greyscale basemaps are helpful when the intended audience already knows the location context, or when significant detail is not important to fulfill the map’s purpose. The simple backdrop adds visual emphasis to your overlay data – especially important for maps produced for entertainment or maps whose primary focus is statistical data (e.g., statistical mortality maps). Choose a light or dark background based on the content and mood of your map, and design overlay data accordingly.

Figure 1.5.3 Light gray (left) and dark gray (right) canvas basemaps

Credit: Screen capture from ArcGIS Pro

Terrain Basemaps

Terrain basemaps are particularly useful when the terrain of the landscape has an important relationship with the data being mapped (e.g., mapping wildfires; hiking maps). Shaded relief also adds visual interest and, when done well, creates a beautiful map. Just be sure to not let the basemap content overwhelm your own data.

Figure 1.5.4 A labeled terrain basemap

Credit: Screen capture from ArcGIS Pro

A comparison of several example basemaps at the same location in Chicago are shown below in Figure 1.5.5. As shown, different basemaps can have vastly different overall looks, as well as differing levels of detail (LOD).

Figure 1.5.5 A comparative view of several basemaps available in ArcGIS Pro: Open Street Map (left), Light Grey Canvas (middle), and Imagery with labels (right)

Credit: Screen capture from ArcGIS Pro

When making a map, your basemap sets the tone - everything else builds from this important beginning.