The height of an obstruction on charts is indicated in feet above what baseline?

The height of an obstruction on charts is indicated in feet above both ground level and sea level. This dual measurement is essential for providing pilots with precise information about obstacles in the airspace to ensure safe navigation and flight operations.

Obstructions can vary significantly in their elevation relative to these two reference points. Ground level measurements typically indicate the height of an obstruction in relation to the terrain directly beneath it, which is useful for low-flying aircraft. In contrast, sea level measurements provide a consistent reference that allows for greater accuracy in high-altitude flight, where fluctuations in terrain may not be as relevant.

It’s important for pilots to consider both levels when assessing potential obstructions, as it helps them to maintain situational awareness and avoid collisions with structures or terrain during their flight paths. Thus, the inclusion of both ground level and sea level references on charts enriches the information available to pilots, aiding in safe flight operations.