Which statement correctly describes the function of onboard instruments in navigation?

Onboard instruments are essential tools that provide pilots with important information about the aircraft's position and navigation status. The correct response indicates that these instruments identify the strength of signals to guide position. This is an accurate representation of their function, as many onboard instruments, like VOR (VHF Omnidirectional Range) receivers and GPS systems, utilize various signals to determine the aircraft's position relative to navigational aids. By analyzing the strength and quality of these signals, the instruments can provide critical data that helps pilots maintain their intended flight path and navigate safely.

In contrast, the other statements do not fully capture the role of onboard instruments. While it might seem that instruments could eliminate the need for external signals, this isn't realistic as they rely on those signals for effective navigation. Instruments do not assess which signals are weaker, as their purpose is more about collecting and interpreting the data rather than comparing signal strength solely. Lastly, stating that onboard instruments indicate only altitude is too limiting, as they provide a wide range of information, including speed, heading, attitude, and navigation data, far beyond just altitude.