Goal-directed video metrology

Abstract

We investigate the general problem of accurate metrology from uncalibrated video sequences where only partial information is available. We show, via a specific example - plotting the position of a goal-bound soccer ball - that accurate measurements can be obtained, and that both qualitative and quantitative questions about the data can be answered. From two video sequences of an incident captured from different viewpoints, we compute a novel (overhead) view using pairs of corresponding images. Using projective constructs we determine the point at which the vertical line through the ball pierces the ground plane in each frame. Throughout we take care to consider possible sources of error and show how these may be eliminated, neglected, or we derive appropriate uncertainty measures which are propagated via a first-order analysis.