[dropcap]T[/dropcap]his project explores the invisible terrain of WiFi networks in urban spaces by light painting signal strength in long-exposure photographs. A four-metre tall measuring rod with 80 points of light reveals cross-sections through WiFi networks using a photographic technique called light-painting.

In order to study the spatial and material qualities of wireless networks, the Immaterials team built a WiFi measuring rod that visualises WiFi signal strength as bars of lights. When moved through space the rod displays changes in the WiFi signal. Long-exposure photographs of the moving rod reveal cross sections of a network’s signal strength.

The WiFi measuring rod is a 4-meter tall probe containing 80 lights that respond to the Received Signal Strength (RSSI) of a particular WiFi network. When they walked through architectural, urban spaces with this probe, while taking long-exposure photographs, they could visualise the cross-sections, or strata, of WiFi signal strength, situated within photographic urban scenes. The cross-sections are an abstraction of WiFi signal strength, a line graph of RSSI across physical space. Although it can be used to determine actual signal strength at a given point, it is much more interesting as a way of seeing the overall pattern, the relative peaks and the troughs situated in the surrounding physical space.

The measuring rod is inspired by the poles land surveyors use to map and describe the physical landscape. Similarly, this equipment allowed the team to reveal and represent topographies of wireless networks. The measuring rod uses a typical mobile WiFi antenna to measure reception, and draw out 4 metre tall graphs of light.

After a week of walking through urban spaces holding and photographing this instrument, they got a much better sense of the qualities of WiFi in urban spaces, its random crackles, bright and dim spots, its reaction to the massing of buildings, and its broad reach through open areas. The resulting images show some of these qualities, and establishes light painting as a brilliant medium for situating visualisations and data into physical world locations and situations.

The light paintings show how WiFi networks are highly local, informal and fragmented, but also illustrate how these networks make up a highly evolved, yet largely inaccessible urban infrastructure that is mainly created by its users. The visualisations demonstrate how WiFi is a part of the urban landscape, and how networks are both shaped by the environment and influence how urban spaces can be used.

‘Immaterials: Light painting WiFi’ points towards potentials for materializing and contextualizing invisible technologies through light painting and visualisations. Hopefully, the film situates the networked city within the everyday environments in which it take place. The light paintings illustrate how the networked city can be both ubiquitous, messy, informal and shows how the invisible landscape of networks is another layer of the dense and complex urban contexts we are already aware of.


‘Immaterials: light painting WiFi’ is created by Timo ArnallJørn Knutsenand Einar Sneve Martinussen. The film joins together TouchYOUrban and Einar’s PhD project on design, technology and city life. Einar is also writes about this work in a chapter for a forthcoming book titled ‘Design Innovation for the Built Environment – Research by Design and the Renovation of Practice’ edited my Michael U. Michael U. Hensel.

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