Qualitative Egomotion (bibtex)

by Cornelia Fermueller, Yiannis Aloimonos

Abstract:

Due to the aperture problem, the only general unambiguous motion measurement in images is normal flow---the projection of image motion on the gradient direction. In this paper we show how a monocular observer can estimate its 3D motion relative to the scene by using normal flow measurements in a global and mostly qualitative way. The problem is addressed through a search technique. By checking constraints imposed by 3D motion parameters on the normal flow field the possible space of solutions is gradually reduced. In the four modules that comprise the solution, constraints of increasing restriction are considered, culminating in testing every single normal flow value for its consistency with a set of motion parameters. The fact that motion is rigid defines geometric relations between certain values of the normal flow field. The selected values form patterns in the image plane that are dependent on only some of the motion parameters. These patterns, which are determined by the signs of the normal flow values, are searched for in order to find the axes of translation and rotation. The third rotational component is computed from normal flow vectors that are only due to rotational motion. Finally, by looking at the complete data set, all solutions that cannot give rise to the given normal flow field are discarded from the solution space.

Reference:

Qualitative Egomotion (Cornelia Fermueller, Yiannis Aloimonos), Technical report, PRIP, TU Wien, 1993.

Bibtex Entry:

@TechReport{TR020, author = "Cornelia Fermueller and Yiannis Aloimonos", institution = "PRIP, TU Wien", number = "PRIP-TR-020", title = "Qualitative {E}gomotion", year = "1993", url = "ftp://ftp.prip.tuwien.ac.at/pub/publications/trs/tr20.pdf", abstract = "Due to the aperture problem, the only general unambiguous motion measurement in images is normal flow---the projection of image motion on the gradient direction. In this paper we show how a monocular observer can estimate its 3D motion relative to the scene by using normal flow measurements in a global and mostly qualitative way. The problem is addressed through a search technique. By checking constraints imposed by 3D motion parameters on the normal flow field the possible space of solutions is gradually reduced. In the four modules that comprise the solution, constraints of increasing restriction are considered, culminating in testing every single normal flow value for its consistency with a set of motion parameters. The fact that motion is rigid defines geometric relations between certain values of the normal flow field. The selected values form patterns in the image plane that are dependent on only some of the motion parameters. These patterns, which are determined by the signs of the normal flow values, are searched for in order to find the axes of translation and rotation. The third rotational component is computed from normal flow vectors that are only due to rotational motion. Finally, by looking at the complete data set, all solutions that cannot give rise to the given normal flow field are discarded from the solution space.", }

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