Data visualization is an emerging domain that is deeply rooted in the tradition of cartography, having evolved to match the quantity and diversity of data we find in today’s technological environment.
In this first post in an ongoing data visualization series, I’ll take a closer look at the New York Times’ Mapping America interactive map of the American census data. This subject also gives me an opportunity to talk briefly about the relationship between cartography and visualization.
As the ancestor of data visualization, cartography was initially used to navigate the land and the sea, to give us an overview of our physical space and help us explore the world more safely. Maps were catalyzers for the development of human societies. Cartography quickly evolved to display not only the shapes of the land but also location-specific data, such as temperature, population or tax income. By overlaying location-specific data on top of topographic maps, cartography provided a tool for everyone to take a step back, and discover their environment in a way they couldn’t imagine before.
Data visualization is all about extending the concept of cartography to mapping any kind of data, whether numerical, spatial, textual or social. As David McCandless said “by visualizing information … we turn it into a landscape,” a virtual landscape that we can then explore to discover hidden trends and patterns that will help us better understand the world we live in.
The New York Times’ “Mapping America” visualization is a good illustration of this strong heritage between cartography and data visualization. It consists of an interactive map of data extracted from the American Community Survey Census, based on samples from 2005 to 2009 and including indicators such as ethnic groups, income, housing, families and education.
From a purely graphical standpoint, the “mapping america” visualization is a very good example of clean, simple, careful design:
- The topographic base is a custom-styled Google Maps overlay. By using subtle shades of blue-gray to denote borders and geological elements, the map blends into the background and lets the viewer focus on the mapped indicators.
- The use of colored dots for ethnicity and income, and colored areas for the other indicators, takes into account population density (with dots) or leaves it out of the equation (with areas) when it is not relevant.
- Details are shown on hovering the mouse, allowing to get the numbers for the indicator and current area. (See this in action on the Times’ website.)
- The interaction is very smooth. Tooltip and areas appear and disappear gracefully.
The presence of controls for interacting with the representation of the data in this visualization is important: you can enter a zip code, city or address to go to a specific location, or change the indicator being displayed without resetting the map. These features might sound simple, as we’re now used to services like Google Maps, but interaction is one of the key elements of data visualization. The user is not only a viewer, he or she becomes an explorer who can use the visualization as a tool to understand what is going on.
The choice of colors in this visualization is also worth mentioning. The palette is based on a playful set of pastel colors (green, blue, yellow, red) which are then adapted for every indicator. Some indicators will use only one color in different shades (education) some will use a gradient between two main colors (when the indicator displays a change). Not only is the type of palette linked to the type of indicator displayed (same color by default, two colors when the indicators denotes a change) but sometimes specific colors are picked for their connotation. For example, the map of households earning under $30K uses red, while the other earning maps use green.
Finally, if you find something interesting using the visualization, you can share a specific URL. This type of targeted sharing encourages discussion and new insights.
Data visualization to empower people
By creating a tool that is easy to use, and that is true to the original data, the New York Times opened up a new range of possibilities. The census data is a cornerstone of social statistics and studies, but without proper tools it is difficult for most people to comprehend. This example taps into the power of visualization: it makes complex information simpler to understand.