Scientists from the reputed Massachusetts Institute of Technology (MIT) have developed an acoustic system named Underwater Backscatter Localization (UBL) that can work like an underwater GPS.
It is not run on batteries but powered by reflecting modulated audio signals to generate binary impulses, as reported in New Atlas.
GPS has always been used on land by people to navigate from one place to another. However, underwater, the radio waves of GPS are scattered by water. This is the reason why submarines use sonar not radio waves underwater to understand their surroundings.
Under the right conditions, acoustic signals can travel for thousands of miles. However, as per the MIT scientists, the acoustic signals generators are power hungry and that acts as a challenge to create underwater GPS. They say that it might not be of significance to nuclear submarines but it matters for the smaller battery-run devices.
The Office of Naval Research and MIT scientists collaborated to overcome this challenge. They took help of the piezoelectric materials that produce electrical charge under mechanical stress. It also creates this charge when subjected to sound waves.
Piezoelectric sensors were used by the team to develop the UBL system. This could use the sound waves as a power source and also selectively reflect back the environmental sound waves as backscatter.
A receiver then picks these sound waves as a binary pattern — 0 is the unreflected sound waves while 1 is for the reflected one. The UBL system can carry information with the help of this binary signal. This information can be used to make a location fix by knowing the time that a sound wave takes to reflect off the sensor and to return to the observation unit.
Another challenge the team faced was the complexity of the underwater environment where the sound waves can bounce off the surface.
The solution to this problem was found to be frequency hopping. The signals were sent in a pattern, across a range of frequencies so that they return at different phases.
This MIT system has passed the proof-of-concept test in shallow waters. The range of this system will be increased before starting the field tests.