What is indicated by an "H" symbol on air navigation charts?

The presence of an "H" symbol on air navigation charts indicates a hospital landing area. This symbol is designed to guide pilots to designated landing zones that are specifically meant for medical emergencies, where quick access to and from hospitals is critical for air ambulances or other emergency medical services. These areas are usually selected for their accessibility, safety, and proximity to medical facilities, ensuring that patients can be transported quickly in urgent situations.

In contrast, the other options do not represent what the "H" symbol signifies on navigation charts. A helicopter airstrip would likely be indicated with different symbols specific to helicopter operations. Highway crossings, while important for other types of navigation, are addressed differently and would not be marked with an "H." Hydroplane zones, which are areas designated for seaplane operations, also have their own specific symbols to avoid confusion. Understanding the meanings of these symbols is crucial for ensuring safe navigation and effective communication in aviation.