Metric rectification for perspective images of planes

We describe the geometry constraints and algorithmic implementation for metric rectification of planes. The rectification allows metric properties, such as angles and length ratios, to be measured on the world plane from a perspective image. The novel contributions are: first. that in a stratified context the various forms of providing metric information, which include a known angle, two equal though unknown angles, and a known length ratio; cart all be represented as circular constraints on the parameters of an affine transformation of the plane - this provides a simple and uniform framework for integrating constraints; second, direct rectification front right angles in the plane; third it is shown that metric rectification enables calibration of the internal camera parameters; fourth, vanishing points are estimated using a Maximum Likelihood estimator; fifth, an algorithm Sor automatic rectification. Examples are given for a number of images, and applications demonstrated for texture map acquisition and metric measurements.