Point based co-linearity is an essential conception in Photogrammetry. But point in photogrammetry means only physical or visible points, such as dots, cross points and corner point etc. Especially in the stage of either analogue or analytical, even digital photogrammetry, the main primitive feature, which can be measured by human operator, is physical point. It can be referred to as Point Photogrammetry contrary to Line photogrammetry, which is proposed and used only in the past about 20 years. For a straight line a coplanar equation is used, where the line on the image lies on the plane, passing through corresponding spatial straight line and the photographing centre in line photogrammetry. All straight lines and curves are normally referred to linear feature rather than point feature in line photogrammetry. The co-planarity can be normally explain as Sa