Study on height measurement from a single view

A simple expression between the ratio of the length of two collinear line segments in a 3D-world space and that in an image plane is presented when the line is normal to the ground or the reference plane. This expression provides a correction term to the linear relation between the ratio of two line lengths, which holds only when the camera axis is parallel to the ground or the reference plane. The correction term is denoted by the inverse of the ratio of X-coordinates in the image plane coordinate system. We examine the accuracy of the method using a lattice pattern images videotaped by a digital video camera. It is recognized that the height of an object is obtained with a good degree of accuracy. We applied our method to height measurement in an actual scene and obtained an unknown height by means of homogeneous coordinate. However there remains some uncertainty to specify points in actual scenes, which leads to errors in height measurements