What is an indication of unacceptable navigation signal coverage?

When evaluating navigation coverage, the absence of a signal received serves as a clear indication of unacceptable navigation signal coverage. Navigation systems, whether VOR, ILS, GPS, or others, rely on receiving a signal to properly guide and provide accurate positional information to the pilot. If there is no signal, it means that the navigation aid is either out of range or malfunctioning, which can lead to a lack of situational awareness and potential navigational errors.

In contrast, strong signal strength typically suggests good coverage, while frequent corrections or consistent course deviations could point to issues like poor signal interpretation or environmental factors affecting signal clarity, rather than an outright lack of coverage. Therefore, the absence of any signal is the most definitive indicator that a pilot cannot rely on the navigation system to provide accurate guidance, making it crucial for safe navigation.