PHD Thesis - Institute for Computer Graphics and Vision - Graz ...

Chapter 7
Living in a piecewise planar world 1
This chapter is designated to explain how the most important tasks in mobile robotics, map
building and localization, can be accomplished using the wide-baseline methods described in
the previous chapters. The approach which is to be presented differs in multiple points from
previous work. One mentionable property of the new approach is that a dense 3D reconstruction
augmented with partial texture is used as world representation. Current vision based SLAM
approaches as described in Chapter 2 use much simpler primitives as world representation, like
3D lines, 3D points or small planar fiducial markers. Irrespective of the primitives used, previous
approaches created only sparse world representations. Throughout this chapter we describe the
advantages of our method over previous methods and explain the new method in detail. We
will show that with our proposed world representation one gains valuable benefits. A second
novelty of our method is that it is possible to do global localization with a single landmark
correspondence only. This enables localization in extreme situations, e.g. when large occlusions
occur. Large occlusions or major temporary scene changes provide a big challenge for state-ofthe-art
localization methods. Robot localization is deeply connected to the underlying world
representation and our method of localizing with a single landmark is made feasible by the new
world representation.
The great potential of the proposed world representation resides in the use of 3D plane
patches as map primitives instead of 3D points and 3D lines. The geometrical constraints introduced
by plane primitives proved extremely valuable, definitely being worth the more complex
map building algorithms. However, by using 3D plane primitives we introduce a strong assumption
into our world representation, that our world is piece-wise planar. The world contains a lot
of structure with cannot be modelled by simple plane primitives. And some may think that this
assumption is too strict. But locally a piece-wise planar approximation will always come close to
the original structure. Moreover man-made places contain at a high degree planar structure and
most robotic platforms are only capable of driving indoors. Furthermore, the 3D reconstructions
used as maps are for robot localization only, thus it is not necessary to model all the details. It
is only necessary to model enough details to allow successful localization. On the contrary the
following particular benefits are gained by the piece-wise planar world description:
Localization from a single landmark: A single 3D landmark is a small planar patch containing
6 3D parameters. This gives more constraints for pose estimation than a single 3D
1 Based on the publication:
F. Fraundorfer and H. Bischof. Global localization from a single feature correspondence. In Proc. 30th Workshop
of the Austrian Association for Pattern Recognition, Obergurgl, Austria, pages 151–160, 2006 [34]
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