GPS (Global Positioning System) relies on signals transmitted by a network of satellites orbiting the Earth. These satellites broadcast precise timing information and their location, which GPS receivers on the ground use to triangulate their own position. While GPS is highly accurate and reliable for most terrestrial applications, it does not work underwater for several reasons:
Signal Attenuation: Water is much denser than air, and it absorbs and scatters GPS signals significantly. As the GPS signals pass from the air into the water, they experience substantial attenuation, reducing their strength and making it challenging for GPS receivers to pick up and process the signals accurately.
Signal Reflection: Unlike air, water can reflect GPS signals, causing multipath interference. When GPS signals bounce off the surface of the water or underwater objects, they create multiple signal paths. This phenomenon can confuse the GPS receiver, leading to errors in positioning.
Signal Speed: The speed of radio waves (used in GPS signals) in water is slower than in the air. This variation in signal speed can introduce timing errors in the GPS calculations, affecting the accuracy of the position fix.
Antenna Location: GPS receivers typically have their antennas placed above the water surface to ensure direct line-of-sight with the satellites. Submerging the antenna underwater disrupts this line-of-sight and reduces the number of satellites that can be seen by the receiver, further degrading accuracy.
Satellite Geometry: The geometry of satellites in view from an underwater location is often not ideal for precise positioning. The limited visibility of satellites can result in weaker signal strengths and less accurate triangulation.
Because of these challenges, GPS is not reliable for positioning and navigation underwater. Alternative methods, such as acoustic positioning systems or inertial navigation systems, are commonly used for underwater navigation and exploration. These systems rely on sound waves or motion sensors to determine the underwater position and orientation.