As to 3-D flow visualization, many methods such as PIV were developed. In these methods, however, it seems to be difficult to understand the geometrical relations of these analyses. Morever, many constraints seems to be imposed on taking pictures of the flow. In this paper, a new method of 3-D flow measurement through descriptive geometry is proposed. From one pair of photos of flow with a square reference, the camera position and 3-D flow velocity can be calculated. The utility of this method is recognized through the measurement of several models. The 3-D flow around a small type of axial flow fan were measured.
