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Estimating diver orientation from video using body markers

Diving is a dangerous activity during which diver's safety is significantly compromised, both due to unpredictable environment and dependence on technical systems for life support. Introducing the concept of a cognitive autonomous underwater vehicle (AUV), that is capable of guiding, observing and assisting the diver at all times, requires precise positioning of the AUV relative to the diver. While diver orientation can be measured locally on the diver and transmitted to the underwater vehicle using acoustic communication channels, the problems of limited bandwidth and communication delay can influence the quality of AUV positioning. Another approach, which is considered in this paper, is to use remote sensing techniques, i.e. mono or stereo camera on board the AUV, to determine orientation of the diver based on markers placed on the divers shoulders. As an initial step, laboratory experiments were conducted where orientation of two physically coupled spherical markers is determined by using mono and stereo camera, and compared to the ground truth orientation obtained from an inertial measurement unit. The obtained results prove the concept in laboratory conditions, with the limitations imposed on the distance of markers relative to the camera.