This paper experimentally analyzes the cognition of open space. Subjects 'walked through' a street simulated by 3-D stereo GIS, and were asked to judge which side of the street has more open space. The result shows that the shape and the position of open space have significant effects on open space cognition. Based on the result, we presented a model explaining the cognition of open space. In the model, we judge whether we are inside or outside of the open space, and the maximum visible area of the open space. It was found that the maximum recognized area is stored constantly while we are inside of the open space.
