Development of an ambulatory physical activity and behavior map monitoring system

To know where a subject is, what he does and how his physiological function responds in daily life, the authors have developed an ambulatory physical activity and behavior map monitoring system, which is a kind of portable microprocessor-based computer. Here the authors used two piezoresistive-type accelerometers to measure a subject´s posture change and physical activities, and a GPS (Global Positioning System) sensor to get the subject´s behavior map. This accelerometer can output the DC component of the acceleration change and by putting this sensor in front of the subject´s waist, his posture change can be detected. This sensor also responds to the subject´s action, and the authors tried to categorize this acceleration data for the subject´s individual actions, like walking, getting on a vehicle and so on. The GPS sensor uses the information sent from space satellites orbiting the Earth, but some positioning error is embedded in this information for military purposes. The authors adopted the DGPS method to obtain more precisely the subject´s location