  This paper presents an efficient annotation procedure and an application
thereof to end-to-end, rich semantic segmentation of the sensed environment
using FMCW scanning radar. We advocate radar over the traditional sensors used
for this task as it operates at longer ranges and is substantially more robust
to adverse weather and illumination conditions. We avoid laborious manual
labelling by exploiting the largest radar-focused urban autonomy dataset
collected to date, correlating radar scans with RGB cameras and LiDAR sensors,
for which semantic segmentation is an already consolidated procedure. The
training procedure leverages a state-of-the-art natural image segmentation
system which is publicly available and as such, in contrast to previous
approaches, allows for the production of copious labels for the radar stream by
incorporating four camera and two LiDAR streams. Additionally, the losses are
computed taking into account labels to the radar sensor horizon by accumulating
LiDAR returns along a pose-chain ahead and behind of the current vehicle
position. Finally, we present the network with multi-channel radar scan inputs
in order to deal with ephemeral and dynamic scene objects.
