A wedge prism also known as Riseley Prism is designed in such a way that there is only a small angle (less than 3 degrees) between its input and output surfaces. A wedge prism can be used either individually to deviate a laser beam by a set angle or in combination with several others to be used in steering applications. It is also used in a similar manner as an angle gauge in variable-radius plot sampling situations. To conduct the sampling of trees, for instance, the wedge prism is used to estimate the base radii of trees by taking advantage of and measuring the optical distortion of the image.