  Autonomous Underwater Vehicles (AUVs) conduct missions underwater without the
need for human intervention. A docking station (DS) can extend mission times of
an AUV by providing a location for the AUV to recharge its batteries and
receive updated mission information. Various methods for locating and tracking
a DS exist, but most rely on expensive acoustic sensors, or are vision-based,
which is significantly affected by water quality. In this \doctype, we present
a vision-based method that utilizes adaptive color LED markers and dynamic
color filtering to maximize landmark visibility in varying water conditions.
Both AUV and DS utilize cameras to determine the water background color in
order to calculate the desired marker color. No communication between AUV and
DS is needed to determine marker color. Experiments conducted in a pool and
lake show our method performs 10 times better than static color thresholding
methods as background color varies. DS detection is possible at a range of 5
meters in clear water with minimal false positives.
