“The complex technologies the networked city relies upon to produce its effects remain distressingly opaque, even to those exposed to them on a daily basis.” – Adam Greenfield (2009)

Immaterials: light painting WiFi film by Timo Arnall, Jørn Knutsen and Einar Sneve Martinussen.

This 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.

This builds on a technique that was invented for the 2009 film ‘Immaterials: the Ghost in the Field’ which probed the edges of the invisible fields that surround RFID readers and tags in the world. It also began a series of investigations into what Matt Jones richly summarised as ‘Immaterials’.

While we were mapping out tiny RFID fields, we wondered what it would be like to apply the light painting process to larger-scale fields of Bluetooth, WiFi, GSM and 3G. What if we built huge light painting apparatus that could map out architectural and city-scale networks in the places and spaces they inhabited? We’re still very interested in understanding radio and wireless networks as one of the substrates essential to contemporary design practice.

We built the WiFi measuring rod, a 4-metre tall probe containing 80 lights that respond to the Received Signal Strength (RSSI) of a particular WiFi network. When we walk through architectural, urban spaces with this probe, while taking long-exposure photographs, we 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.

After a week of walking through urban spaces holding and photographing this instrument, we have 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 light painting is a brilliant medium for situating visualisations and data into physical world locations and situations.

Lots more visualisations and ‘making of’ pictures.

Einar writes more about this in an upcoming article called ‘Making material of the Networked City’ in Design Innovation for the Built Environment – Research by Design and the Renovation of Practice. There is also more detail on the project at the YOUrban weblog.

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This video is about exploring the spatial qualities of RFID, visualised through an RFID probe, long exposure photography and animation. It features Timo Arnall of the Touch project and Jack Schulze of BERG.

The problem and opportunity of invisibility

RFID is still badly understood as an interactive technology. Many aspects of RFID interaction are fundamentally invisible; as users we experience two objects communicating through the ‘magic’ of radio waves. This invisibility is also key to the controversial aspects of RFID technology; once RFID antennas are hidden inside products or in environments, they can be invoked or initiated without explicit knowledge or permission. (See here for more on the invisibility of radio.)

But invisibility also offers opportunities: the lack of touch is an enormous usability and efficiency leap for many systems we interact with everyday (hence the success of Oyster, Suica and Octopus cards). But there is also the ‘magic’ of nearness one of the most compelling experiential aspects of RFID.

As designers we took this invisibility as a challenge. We needed to know more about the way that RFID technology inhabits space so that we could better understand the kinds of interactions that can be built with it and the ways it can be used effectively and playfully inside physical products.

The experiments

In order to study the readable volume around an RFID reader, we built experimental probes that would flash an LED light when they successfully read an RFID tag. The readable volume is not the same as the radio field, instead it shows the space within the field in which an RFID tag and an RFID reader will interact with each other.

One version of our probe containing a tag and LED light connected to the RFID reader that is being studied.

In a dark room, the probes were moved around the various RFID tags and readers that we wanted to study, with a camera taking long-exposure photographs of the resulting patterns of light. In this way we could build up layers by slicing through the field in different ways, creating animations that clearly reveal the spatial properties of this interaction.

These experiments were carried out in order to help us flesh out our own models of the technology, and were not intended to be scientifically accurate. So although they accurately reflect the behaviour of the technologies in the situations that we work with, there were no controlled environments or settings for generalisable technical accuracy.

Innovations ID 20

The Innovations ID 20 RFID reader has become one of the standard components in a lot of our work, it is small, robust and relatively cheap. So it has been very important for us to gain an understanding of the readable volume it produces when we embed the reader inside products such as Sniff and Skål.

Details: Innovations ID20 low-frequency EM4102 reader, 20mm circular EM4102 tag.

The resulting visualisation shows the way in which we have mapped the boundary of the readable volume, although a tag will read anywhere inside this, we have only mapped the edge for the sake of clarity. From the animation (see the video) we start to clearly see that the readable volume is made up of a strong central sphere, accompanied by a smaller lobe that surrounds the edge of the reader.

Oyster card

Mifare cards are one of the largest public applications of RFID, used in many transit systems around the world such as the Oyster and Suica cards. It has become common to have to touch in and touch out of subway stations, and many people have become accustomed to this interaction. So what does the readable volume around an Oyster card look like?

Details: Standard Mifare Oyster card, probed with a Sonmicro high-frequency reader.

With a square antenna inside the Oyster and the Sonmicro reader, we get an elongated main volume, accompanied by long skinny lobes on each edge of the card. This looks very different from the ID 20 mapping.

Orientation

The first two mappings held the reader and the tag parallel to each other, but we predicted that there would be a higher degree of complexity in the relationship if the tag and the reader moved in different orientations. The rig below was built so that we could control the angle between the reader and the tag, which moved along the surface of the table.

Details: Innovations ID20 low-frequency EM4102 reader, 50mm circular EM4102 tag.

There is clearly enormous physical complexity in this relationship, in the animation we can see the volume growing and shrinking, lobes turning into spheres, and vice-versa. But the animation gives us a very clear picture of the ‘throw’ of the reader onto a single two-dimensional plane, almost like looking at it as a torch.

Parallel and perpendicular

To show the two extremes of the relationship between orientation and the readable volume, we created two mappings, one with the tag parallel to the reader, and the other with the tag perpendicular. We mapped them using two different colours of LED: green for parallel and red for perpendicular.

Details: Innovations ID20 low-frequency EM4102 reader, 20mm circular EM4102 tag.

This image is a composite of the two mappings (see the video for animations of the two mappings separately) and it is clear that the readable volume is significantly different. When the tag is perpendicular to the reader, there is a sizeable gap in the middle of the reader where the tag will not read, creating two readable volumes side by side.

Conclusions

We have been continually challenging the ways in which RFID technology has been framed. It is incredible how often RFID is seen as a long-range ‘detector’ or how little relevant information is contained in technical data-sheets. When this information is the primary material that we are working with as designers, this is highly problematic. By doing these kind of experiments we can re-frame the technology according to our experience of it, and generate our own material knowledge.

One of the early motivations in this project was the way in which the animations really captured our tacit, embodied knowledge of the readable volume in a visual way, it was almost as if you could wave your hand through the floating green LEDs and feel them. Of course we had felt it hundreds of times in experimenting with tags and readers, but we had never seen it captured in an image, in a way that was communicable to others without having them try an interactive demonstrator. With this visual material, we can communicate about RFID in ways that we couldn’t previously.

So we hope that this work goes some way towards building better spatial and gestural models of RFID, as material for designers to build better products and to take full advantage of the various ways in which spatial proximity can be used. And with this better understanding we hope to be able to discuss and design for privacy and the ‘leakage’ of data in a more rigorous way.

Field icon

Download a PDF file of the RFID icon.

This RFID icon is based on the shape of the ‘readable volume’. Created by Timo Arnall & Jack Schulze, it is licensed for use under a Creative Commons Attribution 3.0 Unported License.

Go ahead and use it!

Credits

The project was made by Timo Arnall and Einar Sneve Martinussen from AHO and Jack Schulze from BERG. Thanks to Jørn Knutsen for help in building the rigs.

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Right now I am sitting near fourteen objects sending and receiving radio signals, from Oyster cards to mobile phones and wireless routers in a multitude of overlapping and competing fields. Here we are creating communicative material that uses dashed-line abstractions to visualise the presence of wireless technologies in the everyday environment. What if we could see every field produced by an Oyster card or NFC enabled mobile phone for instance?

Using simple abstractions such as the dashed line and the kinds of visual language that we have previously proposed for RFID allow us to quickly communicate aspects such as the spatial properties of wireless technologies that are often overlooked. I’ve been using these images in presentations for a while, to sensitise designers and students to the spatial and embodied properties of RFID, Bluetooth and WIFI.

We are also experimenting with video, where the visualisations are part of an environment in a moving sequence. This is looking like a useful technique for making visual explanations of invisible materials.

Here are more images:

NFC phones and contactless cards.

NFC phones.

Wifi and bluetooth.

An NFC-enabled bus timetable.

An NFC-enabled ‘smart poster’.

An Oyster card reader and cards

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This collection of ‘vernacular’ designs for RFID-based interfaces is extremely interesting for us, as we delve deeper into the visual representation of emerging technologies.

If you have images of good, bad and especially odd interfaces where interaction with an RFID tag or NFC mobile phone is indicated with an icon or an interestingly designed physical enclosure, please add it to the pool by tagging it ‘touch interface’.

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I’ve had trouble justifying my excitement about this intricate visual detail, so I thought it would be good to collect a bunch of examples from over fifty years of information design history, to show it as a powerful visual element in ubicomp situations.

Even though the dashed line has emerged from a designer’s shorthand and from the limitations of monotone printing techniques, it has a clear and simple visual magic, the ability to express something three- or four-dimensional in two dimensions.

The dashed line as hidden geometry

Examples from Open Here: The Art of Instructional Design, Paul Mijksenaar, Piet Westendorp, 1999.

The dashed line as movement

The line is used to indicate temporal positions:

Examples from Open Here: The Art of Instructional Design, Paul Mijksenaar, Piet Westendorp, 1999.

The dashed line as paths

Very similar to the representations of movement, but the line is used as the path itself:

Examples from Open Here: The Art of Instructional Design, Paul Mijksenaar, Piet Westendorp, 1999.

A more modern image showing an overview of Auto ID RFID supply chain management, by Xplane:

Colin Ware defines dashed, dotted or wavy lines as linking lines:

“A linking line between entities represents some kind of relationship between them. A line linking closed contours can have different colours or other graphical qualities such as waviness, and this effectively represents an attribute or type of relationship.”

From the perceptual syntax of diagrams in Information Visualisation: Perception for Design, Colin Ware, 1999.

The dashed line as expectation

I’ve spoken to some people that have made an association between the dashed line and an ellipsis. This example is taken from the Mac OS X interface, conventionally used to indicate that the action will be followed by another action.

The dashed line as ephemeral material

Examples from Open Here: The Art of Instructional Design, Paul Mijksenaar, Piet Westendorp, 1999.

The dashed line as border or seams

A table of commonly used conventions from Information Graphics, Robert Harris, 1996.

Other examples

This is an example of dashed lines in information design from The Visual Display of Quantitative Information, Edward Tufte, 1983. I get the sense that Tufte prefers a simple, solid line, considering the overuse of patterns a form of chart-junk:

And lastly, an interesting thought from a conversation with Dave Gray, of Xplane and Communication nation:

“I think of lines: double-line, solid, dashed, dotted Similar to typeface conventions such as black, bold, regular, light. It’s a matter of emphasis. The thicker and more solid the line, the stronger the emphasis. A dotted line usually does not indicate “cut here” unless it is combined with a scissors icon. I think that trying to make a direct connection between the dashed line and what it represents may be a red herring. Think of a map, for example: Whether type is bold, all caps, or light relates directly to the designer’s decisions about emphasis, but I am not sure it relates so directly to the subject matter. There are a few direct correlations of this type: for example, type representing water is usually set in italic. I like your use of the dashed line – it is clear that they serve as a guide and invitation to “place things there”.”

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