Michael R. McCarthy

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In this paper we present a user-centric position sensing system that is based on asynchronous, independent ultrasonic beacons. These stationary transmitter units are small, cheap to manufacture, and have power requirements low enough to run each from a small solar cell and a nearby light source. Each beacon is programmed to emit a short, 40 kHz ultrasonic(More)
Ubiquitous computing technologies which are cheap and easy to use are more likely to be adopted by users beyond the ubiquitous computing community. We present an ultrasonic-only tracking system that is cheap to build, self-calibrating and self-orientating, and has a convenient form factor. The system tracks low-power tags in three dimensions. The tags are(More)
Pauses in distributed groupware activity can indicate anything from technical latency through infrastructure failure to a participant's thoughtful contemplation. Unraveling these ambiguities highlights mismatches between unseen off-screen activities and on-screen cursor behaviors. In this paper we suggest that groupware systems have typically been poor at(More)
In this paper we present a novel positioning technique that is based on transmissions from independent ultrasound beacons. These unsynchronised beacons emit narrow-band ultrasonic pulses and do not use any other medium, such as radio frequency or infra-red. A passive mobile positioning unit locates itself using the signatures of the received ultrasound(More)
In this paper we present a study on how to estimate the position of a mobile receiver using ultrasonic beacons fixed in the environment. Unlike traditional approaches, the ultra-sonic beacons are independent, and positioning is performed by measuring the Doppler shift within their observed periods. We show that this approach allows us to deduce both(More)
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