UW develops first underwater 3D positioning app for smart devices

A team at the University of Washington has developed the first underwater 3D-positioning app for smart devices.

“Mobile devices today can work nearly anywhere on Earth. You can be in a forest or on a plane and still get internet connectivity,” said lead author Tuochao Chen, a UW doctoral student in the Paul G. Allen School of Computer Science & Engineering. “But the one place where we still hadn’t made mobile devices work was underwater. It’s kind of the final frontier.”

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Above water, GPS relies on a vast satellite network to locate mobile devices with radio signals. Underwater, these signals quickly fade.

However, when the new devices are used, at least three divers within 100 feet or less of each other can track each other. The existing speakers and microphones on their smart devices are able to contact each other, and the app tracks each user’s location relative to the leader.

Often swimmers have limited visibility. The new app has value for scuba divers and snorkelers because it helps them find each other in an emergency.

Previous underwater positioning systems have relied on strategically placed buoys, but these systems are expensive and cumbersome to deploy. The UW team found that such buoys aren’t necessary.

With the app, if the dive leader has at least one other diver visible, the group’s devices can send acoustic signals to each other through their microphones and speakers and use the timestamps to estimate each diver’s distance. Based on these distances, the app can estimate the group’s formation and each diver’s location. If a device also tracks depth, as sport monitors like the Apple Watch Ultra or the Garmin Descent do, the system can locate divers in 3D.

The app needs at least three devices in its network to function.

The study builds on a previous breakthrough from the lab called AquaApp, which allows divers to send messages to each other underwater.

“This and AquaApp can be used together,” said author Justin Chan, a UW doctoral student in the Allen School. “For example, if the dive leader finds someone going the wrong way, the leader can send an alert: ‘Hey, you’re going out of range. You need to come back.’ Or if a diver is running out of gas, an SOS can let the team find the person quickly even in murky water.”