Sensing your Friends’ Locations via the Sense of Touch

Imagine visiting a crowded place with a bunch of friends. Wouldn’t it be great to unobtrusively stay aware of where they are? Thanks to 3G, GPS, and powerful handhelds, today it is perfectly possible to share the location in such a mobile context.

A remaining problem is how to present the friends’ locations to the user. Instead of constantly pulling the device out of your pocket you might rather want to enjoy the event. The environment may be noisy and crowded, making the interaction with the device difficult in general.

We therefore developed a system that displays the location of friends via the sense of touch. Specifically, we aimed at conveying the direction and the distance of a number of friends, so the user would have a rough idea of where her/his friends are.

For communicating via the sense of touch we used a tactile belt. A tactile belt is a belt that comprises a number of vibration motors (Tactors), which are distributed all around the waist when the belt is worn. It has been demonstrated by other research groups that users can easily interpret the vibration patterns as pointing directions. If for example the front vibration motor is turned on the belt seems to point forward.

In our system we used this to inform the wearer in which direction a friend is. Since we wanted to display the direction of more than one friend we iterated through the friends. Each friend’s direction is displayed for a short time before the system switches to the next friend.

To convey a location we added a distance cue into the tactile signal. From the direction and the distance we assumed the user could get a rough understanding of the friend’s location. We tested three different ways of encoding the friend’s distance in the vibration.

In the rhythm-based distance encoding the belt would pulse a number of times into the direction of the friend. The number indicates the distance. The more pulses, the further the friend is away.

In the duration-based distance encoding the belt would use a single pulse to display the friend’s direction. The distance is encoded in the length of the pulse. The longer the pulse is the further the friend is away.

In the intensity-based distance encoding the belt would use a single pulse to display the friend’s direction. The distance is encoded in the pulse’s intensity. The further the friend is away, the less intense the pulse becomes.

In an experiment we compared the three distances encodings to find out how accurate and intuitive they are. The rhythm-based encoding allowed the most accurate and intuitive distance perception. However, the intensity-based and the duration-based distance encodings made it subjectively easier to judge the friend’s direction.

Altogether, we could show that providing a rough estimate of e.g. the location of people via the sense of touch is possible.

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