We present Loc-NeRF, a real-time vision-based robot localization approach
that combines Monte Carlo localization and Neural Radiance Fields (NeRF). Our
system uses a pre-trained NeRF model as the map of an environment and can
localize itself in real-time using an RGB camera as the only exteroceptive
sensor onboard the robot. While neural radiance fields have seen significant
applications for visual rendering in computer vision and graphics, they have
found limited use in robotics. Existing approaches for NeRF-based localization
require both a good initial pose guess and significant computation, making them
impractical for real-time robotics applications. By using Monte Carlo
localization as a workhorse to estimate poses using a NeRF map model, Loc-NeRF
is able to perform localization faster than the state of the art and without
relying on an initial pose estimate. In addition to testing on synthetic data,
we also run our system using real data collected by a Clearpath Jackal UGV and
demonstrate for the first time the ability to perform real-time global
localization with neural radiance fields. We make our code publicly available
at https://github.com/MIT-SPARK/Loc-NeRF