How to Make a Smell Map
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Sniff Map

Smell is a sense that’s hard to record and depict visually. Designer Kate McLean is tackling that challenge. She’s led odor-mapping walks in cities around the world like Glasgow, Edinburgh, Amsterdam, Newport, Rhode Island and Paris.

Using the captions on geotagged photos on visual social networks, she’s been able to map urban aroma distribution. She calls the results smell maps.

What is a Sniff Map?

Although humans are capable of distinguishing over a trillion different smells, useful maps of urban aromas have been elusive. Color maps can be made using cameras and monitors; but smell mapping requires close contact between the human nose and a sensor that records odors rather than photons.

Artist and lecturer Kate McLean has been surveying the smellscapes of cities for the past decade, collecting data and translating its sensory qualities into visual representations. These maps, which are ephemeral snapshots of a city’s smells at one point in time, highlight the unique olfactory qualities that make a place.

To produce these olfactory data visualizations, McLean leads small armies of urban explorers on “smellwalks” around cities and logs the olfactive information that they encounter. She then transforms these findings into maps, like the ones above of London and Barcelona. Here, auto emissions (such as car exhaust and gasoline) follow major roadways, while nature smells—like flowers and grass—are concentrated in parks and green spaces.

How to make a Sniff Map

The first step in making a smell map is to decide what scents you want to map. For her exhibition Scratch ‘N Sniff NYC, Nicola Twilley used a crowd-sourced selection of smell biases from visitors to the gallery and mapped them in accordance with dominant odor perception frameworks in different New York City neighbourhoods.

In a paper published earlier this year, neurobiologists Rafi Haddad and colleagues analysed the characteristics of 450 odours and translated them into locations on a multidimensional map, much like similar colors are grouped together on a rainbow. The team also predicted where a particular smell would be located based on its chemical makeup and previous studies showing that similar odours activate similar brain responses in animals.

UK-based designer Kate McLean has also been creating scent maps, documenting and interpreting the perfumes, odours and fragrances that make up a given city’s “smellscape.” Her sensory renderings reveal more about a place than might otherwise be obvious from the naked eye. Spicy, exotic odours may suggest a diverse cultural mix, musty and dank smells can signal decay or disuse, while floral and botanical aromas can indicate a green and lively area.

Why Sniff Maps are important

Smell Maps allow us to see and describe our shared environment in a new way. They can also help reveal our olfactory biases, which are influenced by personal and cultural context, but may also be based on fundamentally human olfactory capabilities, preferences, and analogies.

Sniff Maps are particularly valuable because smell is so closely tied to perception and behavior across the animal kingdom—just consider the way mosquitoes are drawn to humans by their odor, which can be predicted by computer programs like the Principal Odor Map (POM). These maps could also open up new doors in science, such as the possibility of creating an olfactory AI program that can be used to predict whether or not a molecule is likely to smell good.

While maps are made of permanent features, smell-maps document odiferous landscapes that exist only at the moment of their creation. This makes them more like an aerial view than a traditional map, and it’s one that Kate McLean has been exploring on smell walks around Edinburgh, Boston, and now New York City.

How to use Sniff Maps

The human nose can distinguish more than a trillion different smells, but useful maps of urban odorscapes have been difficult to produce. This is due to a host of factors including the inaccuracy of odor sensors (smell “cameras” and monitors are currently unavailable) and the inability to record or depict odors at a distance.

Rossano Schifanella is an Assistant Professor at the University of Turin in Italy, where he designs new mapping tools that are aware of people’s multi-sensory experience. He uses these tools to create visualizations that explore urban environments from a new perspective.

McLean has led small armies of urban explorers on “smell walks” around the world, collecting data to make smell maps for cities including Boston, Edinburgh, London, Amsterdam, Pamplona, and Newport, Rhode Island. During these walks, participants catalog the smells they encounter with a device called the Sniffer. This Sniffer has two modes: one that detects organic waste, and another that detects inorganic waste. The resulting data are displayed in a map that geo-visualizes the shape of a city.