PhotoMeter: Easy-to-use MonoGraphoMetrics

MonoGraphoMetrics is the science of computing 3D measures from a single image. Several recent research activities have produced theoretical principles and practical tools for extracting 3D measures from uncalibrated photographs. These tools require that the user identifies configurations of edges, which are used to establish constraints or to identify planes in the scene. The process involved is often laborious and its application is limited to images where the required configurations of edges are visible. In contrast, the work presented here is limited to photographs taken with a calibrated camera, oriented horizontally, at a known height above the floor. Under these conditions, a single mouse click provides enough information to compute the 3D position of any point p in the coordinate system of the camera, provided that p and its projection f on the floor can be identified in the image. With this approach, a novice user of our PhotoMeter system can easily measure dimensions and positions of windows, doors, pieces of furniture, and even people with one or two mouse clicks per measurement. The paper describes the geometric computation of the measurements, the user interface, and a study of how errors in the height and horizontal orientation of the camera affect the measurements