The Node Network: Intangible Interface

One component of Loca is a network of nodes, enabling the Loca art group to track and communicate with passersby via their mobile phone without their permission or knowledge, so long as they have a Bluetooth device set to discoverable. Over 7 days at its premier full presentation at ISEA2006 and ZeroOne in August 2006 more than two thousand five hundred people were detected more than half a million (500,000) times, enabling the team to build up a detailed picture of their movements, and send them messages responding to their location via 'Bluejacking' (unsolicited messages sent to Bluetooth devices).

Loca deploys a cluster of interconnected, self-sufficient Bluetooth nodes in an urban environment, working independently from mobile phone companies and other service providers. Each node is built using old phones and readily available, cheap parts. Software is by the Loca team: they run a modified version of ContextPhone, gathering data and uploading it to a modified version of the Aware platform. The node casings are cast in concrete for durability in the urban environment, and to visually blend in with the everyday infrastructure of the city. External batteries inside the nodes mean devices can run for several days, and a production line is created to continually recharge and replace batteries, and to reset the software. The nodes are deployed at key points across the city, chosen to yield the most interesting results. New nodes can be added or old ones removed to create a surveillance swarm.

Inferences based on analysis of the data (server-side) guide communication with the Bluetooth users, via 'Bluejacking'. Nothing stops you from scanning, in fact it is part of the protocol, whereas GSM you are not allowed. All people need to participate is a Bluetooth device set to discoverable.