location – Martin's Blog

Being able to sense the location of people can be beneficial if you visit a crowded, noisy, and chaotic place with your friends, such as a festival. Usually, for a good nightly experience, it is important that the group stays together. However, when everyone has different needs at different times (getting food, visiting the lavatory …) it becomes increasingly challenging to keep everyone together, which is contradictory to a joyful night out.

Thanks to GPS and mobile Internet, different solutions exist where the mobile phone of each friend communicates its GPS location to a server, which then forwards the location to all the other friends’ mobile devices. The problem with existing implementations, such as Google Latitude or Glympse, is that they use maps to communicate these locations. It is more than just inconvenient to read a map while walking through a dense crowd.

We therefore investigated whether the skin can be used to communicate the location of people and therefore be turned into a “friend sense”. Our solution is quite simple, as we wanted to implement it on everyday smartphones. The user can select to “follow” one of the friends. The application then calculates the relative location of this friend, such as “left-hand side”. This information is then encoded into vibration patterns. By learning the meaning of the patterns, the user can understand where the friend is without even taking the device out of the pocket.

We tested this concept on a festival with two groups à 6 friends each. Three of each group could sense the others while three only shared their locations. Over the night we repeatedly probed the participant’s mood and the subjective level of attention they devoted to keeping the group together. In both cases, we could find statistically significant differences between users and non-users of the “friend sense”. The friends that were able to sense the other were more relaxed, felt more confident, and subjectively devoted less attention to keep the group together.

More details on FriendSense and this study can be found in A Tactile Friend Sense for Keeping Groups Together, a work-in-progress to be published as part of the extended abstract of the CHI ’11 conference.

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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.