Many people come to learn and understand the landscape of their region while looking out the window of an automobile. How much can they see, and how does this affect their perception of the landscape? How might a map of visible landscapes be useful?

Using GDAL and an approximately 30 m digital elevation model, I generated viewsheds at 1 km intervals along every state and federal highway in Washington state, USA. This resulted in over 11,000+ individual viewsheds. I then summed these to create a “cumulative viewshed” showing the landscapes estimated to be most visible to motorists in the highway network.

High mountain peaks, long ridgelines, some valleys, and areas of open water are the most visible. These landforms may constitute landmarks that shape the mental maps of residents. Weighting the viewsheds by traffic counts gives an even more nuanced idea of the landforms that perhaps most strongly form Washington residents’ understandings of their state. Also of interest are the areas that are not seen: expansive areas of the Cascade Range and the rolling hills of the Palouse. The invisibility of these landscapes might contribute to difficulty with understanding their size or the activities occurring therein.

Cumulative viewsheds like this can help cartographers understand which features should be labeled most prominently on print and digital maps. Similarly, they might be able to inform augmented reality displays to increase the geographic literacy of travelers. By intersecting the road network with the cumulative viewshed, it’s also possible to identify potentially scenic viewpoints for tourists.

To explore the full set of maps and analysis, please see the open access paper What can we see from the road? Applications of a cumulative viewshed analysis on a US state highway network.