In mobile and ubiquitous computing environments, acquisition of contextual information about a user situation is necessary to provide useful services. Although the definition of user context may change according to the situation or the service used, contextual information about who, where, and when are considered to be essential. We have built a test bed with multiple sensors: floor pressure sensors, RFID (radio frequency identification) tag systems, and cameras, to carry out experiments to detect the positions of users and track their movement. The test bed is described and experimental results are presented. By using the background subtraction method, which is conventional and effective, we found moving objects can be extracted under limited conditions in real time.