  Due to their ubiquity and long-term stability, pole-like objects are well
suited to serve as landmarks for vehicle localization in urban environments. In
this work, we present a complete mapping and long-term localization system
based on pole landmarks extracted from 3-D lidar data. Our approach features a
novel pole detector, a mapping module, and an online localization module, each
of which are described in detail, and for which we provide an open-source
implementation at www.github.com/acschaefer/polex. In extensive experiments, we
demonstrate that our method improves on the state of the art with respect to
long-term reliability and accuracy: First, we prove reliability by tasking the
system with localizing a mobile robot over the course of 15~months in an urban
area based on an initial map, confronting it with constantly varying routes,
differing weather conditions, seasonal changes, and construction sites. Second,
we show that the proposed approach clearly outperforms a recently published
method in terms of accuracy.
