Autocalibration from Tracks of Walking People

It has been shown that under a small number of assumptions, observations of people can be used to obtain metric calibration information of a camera, which is particularly useful for surveillance applications. However, previous work had to exclude the common criticial configuration of the camera’s principal point falling on the horizon line and very long focal lengths, both of which occur commonly in practise. Due to noise, the quality of the calibration quickly degrades at and in the vicinity of these configurations. This paper provides a robust solution to this problem by incorporating information about the motion of people into the estimation process. It is shown that under the assumption that people walk with a constant velocity, calibration performance can be improved significantly. In addition to solving the above problem, the incorporation of temporal data also helps to take correlations between subsequent detections into consideration, which leads to an up-front reduction of the noise in the measurements and an overall improvement in auto-calibration performance.