Most of previous surveys of tourist activities using GPS devices have focused on where tourists visit and how long they stay, but not on what they actually do at each location. Thus, we have attempted to investigate the relations between the tourists' actual activities and their spatio-temporal data. In this paper, we conducted some experiments at a zoological park to build statistical methods for estimating whether a tourist is viewing an exhibition or not from his/her GPS logs. The result shows that their walking speed seems critical for the estimation, and, by considering additional parameters, we can estimate precisely whether 20s tourist is viewing or not.