Resumen de Real-time Outdoor Positioning System Exploiting Ultrasonic Wireless Sensor Nodes
Young-yeol Choo, Eung-Joo Lee, Sooyol Ok
In this paper, we present a passive positioning system using Cricket Mote sensors. In order to improve accuracy of the passive system, the transmission speed of ultrasound was compensated according to air temperature at the moment. Upper and lower bounds of a distance estimation were set up through measuring minimum and maximum distances that ultrasonic signal can reach to. Distance estimations beyond the upper and the lower bounds were filtered off as errors in our scheme. We measured distances with Cricket nodes at several points which are 50 cm apart respectively and compared them with real distances to compensate the deviation at each point. A filtering method was proposed to discard error data during movement of target device. At outdoor tests, average location error and average location tracking period were 3,5 cm and 0,5 second, respectively, which outperformed original Cricket location system.
