  We present a complete map management process for a visual localization system
designed for multi-vehicle long- term operations in resource constrained
outdoor environments. Outdoor visual localization generates large amounts of
data that need to be incorporated into a lifelong visual map in order to allow
localization at all times and under all appearance conditions. Processing these
large quantities of data is non- trivial, as it is subject to limited
computational and storage capabilities both on the vehicle and on the mapping
backend. We address this problem with a two-fold map update paradigm capable
of, either, adding new visual cues to the map, or updating co-observation
statistics. The former, in combination with offline map summarization
techniques, allows enhancing the appearance coverage of the lifelong map while
keeping the map size limited. On the other hand, the latter is able to
significantly boost the appearance-based landmark selection for efficient
online localization without incurring any additional computational or storage
burden. Our evaluation in challenging outdoor conditions shows that our
proposed map management process allows building and maintaining maps for
precise visual localization over long time spans in a tractable and scalable
fashion.
