Is altitude usually referenced in MSL or AGL on approach charts?

Altitude on approach charts is typically referenced in Mean Sea Level (MSL). This standardization allows pilots to have a consistent frame of reference when navigating, as MSL is a fixed point that can be universally understood, irrespective of local terrain variations. Most approach procedures, including altitudes for holding patterns, minimum altitude for approaches, and minimum safe altitudes are designated in MSL to ensure safety and proper separation from terrain and obstacles.

While there are instances where specific information might be referenced in AGL (Above Ground Level) for certain visual cues or when discussing specific altitude clearances in relation to nearby terrain, the fundamental altitudes on approach charts—and many other aviation charts—are presented in MSL to maintain clarity and safety across diverse flight operations and environments.