GPS system satellites transmit their signals on two carrier waves 1575 MHz and 1227 MHz. What does commercial aviation use?

In the context of commercial aviation and GPS technology, the correct understanding revolves around the use of the L1 frequency, which operates at 1575 MHz. This frequency is primarily used for civilian applications, including commercial aviation. The L1 signal includes a specific code called the C/A code, which stands for Coarse/Acquisition code. This code allows for navigation and position fixing for aircraft and other civilian users.

The use of only the 1575 MHz carrier wave and one code is specifically designed to meet the needs of civilian aviation, providing appropriate accuracy while also being less complex than using multiple frequencies. This makes it more accessible for standard aviation applications without requiring additional, more advanced capabilities found in other services.

In contrast, the other frequencies and codes that exist (such as the L2 frequency at 1227 MHz) are mainly used for more specialized applications or for military purposes, where higher precision and redundancy are required. Therefore, commercial aviation typically employs the L1 frequency along with the C/A code for effective operation and navigation.