  Powered wheelchair users encounter barriers to their mobility everyday.
Entering a building with non barrier-free areas can massively impact the user
mobility related activities. There are a few commercial devices and some
experimental that can climb stairs using for instance adaptive wheels with
joints or caterpillar drive. These systems rely on the use for sensing and
control. For safe automated obstacle crossing, a robust and environment
invariant detection of the surrounding is necessary. Radar may prove to be a
suitable sensor for its capability to handle harsh outdoor environmental
conditions. In this paper, we introduce a mirror based two dimensional
Frequency-Modulated Continuous-Wave (FMCW) radar scanner for stair detection. A
radar image based stair dimensioning approach is presented and tested under
laboratory and realistic conditions.
