What do Directional Indicating Systems utilize for heading reference?

Directional Indicating Systems utilize magnetic heading information obtained from two independent compass systems to provide an accurate and reliable heading reference. By drawing data from two separate compass systems, these systems enhance reliability and reduce errors that can occur due to magnetic variations or disturbances. This redundancy allows for cross-verification of the heading information, ensuring that navigators can trust the data they receive, which is crucial for effective navigation and flight safety.

In contrast, utilizing a single compass system may lead to inaccuracies if that system encounters failure or interference. Altimeter data and atmospheric pressure readings relate more to altitude and environmental factors rather than heading determination, which is not applicable in the context of a directional indicating system. Thus, the correct choice emphasizes the importance of utilizing information from independent systems to enhance navigational accuracy.