Underwater Localization - More than Localization Underwater
Abstract: Underwater localization (UWL) is a key component in most underwater communication applications. The absence of GPS reception underwater and the reliance on ranging information from anchor nodes make the UWL problem similar to that of indoor localization. But UWL also poses a number of additional challenges. Ranging estimates are noisy due to the channel large delay spread and attenuation of the direct path, acceleration measurements required for location tracking are effected by fast time-varying orientation changes, and nodes are constantly moving due to the irregular water current. Taking these specific features of UWL into account, in this talk we will present our approach for localization and tracking underwater.
Our UWL algorithm assumes the assistance of a dead-reckoning (DR) system to obtain short-term motion estimates, and exploits the permanent motion of nodes for multiple range measurements, and the dependency between the drift motion of network nodes. As an alternative to using gyro-compass for DR, especially for shallow water where vessel motion is affected by waves, we use only a single accelerometer device to compensate for the vessel's time-varying pitch angle. Furthermore, our algorithm classifies time-of-arrival (ToA) measurements to reduce ranging errors due to non-line-of-sight links. We will present results from four different experiments conducted in Israel and Singapore, which demonstrate the performance of our UWL solution in a real sea environment.