A method for estimating Lambertian surface shape from shading information is developed with the aid of a coordinate system having one axis in the assumed direction of the height source. A physical interpretation for the gradient direction is proposed which relates to the surface tilt at the given point. This is achieved by using an approximation of the surface by a spherical patch. Improved methods of estimating the light source direction are also presented. This work represents an improvement on the methods proposed in [1, 2, and 3].