This paper aimed to demonstrate how location-based services were implemented in ubiquitous outdoor ecological learning system. In an elementary school in northern Taiwan, two fifth grade classes on an ecology project were randomly selected: The experimental group could access the ecological learning system on hand-held devices while the control group was guided by a human guide. Flow Learning was adopted as the teaching scheme for this study. We seek to arouse students' motivation to study first, have them focus next, create opportunities for acquiring knowledge by directly observing the phenomenon to be studied, and finally encourage students to share what they have learned. The results showed that the experimental group outperformed the control group on the ecological knowledge test. Furthermore, the students in the experimental group felt satisfied with the ecological learning system supported by positioning systems. The pedagogical implication of this study is that students need direct experience to gain an understanding of a certain topic. (Contains 4 tables and 16 figures.)