Empirical studies of human behavior have been developed mainly using methods of interview or questionnaire by researchers themselves. These studies have successfully obtained adequate results. To observe the behavior of many subjects at once, for many hours and in a wide area however, an alternative technological method is required. The purpose of the authors' work is to develop a better objective method based on measurements, observations and experiments to clarify human behavior in urban environments. The purpose of this paper, as a first step, is to show the availability of research methods concerning children's behavior after school in a suburban city district. The authors asked each primary schooler to wear a compact Global Positioning System receiver after school and to act casually. The collected spatio-temporal data using the Geographical Information System was also analyzed by developing a denoising technique. As a result, the authors clarified the behavior patterns of 35 primary schoolers' regarding transportation devices, travelling routes, distances, time to arrive home and duration of outdoor activity. In conclusion, the authors showed the validity of a research method concerning the collective subjects' behavior for a long period and in a wide area based on more reliable data using the Global Positioning System.