Why does GPS work in a tunnel but satellite radio doesn?

GPS can work in a tunnel because it relies on signals from multiple satellites, which can sometimes penetrate through the tunnel’s structure, particularly if there are openings or if the tunnel is not too deep. Additionally, some GPS devices can utilize inertial navigation systems to estimate position when satellite signals are weak. In contrast, satellite radio requires a clear line of sight to satellites for signal reception, making it ineffective in tunnels where the signal is obstructed. Therefore, while GPS may provide limited functionality, satellite radio typically does not operate at all in such environments.