In a non-precision approach (that is when no electronic glideslope is provided), the minimum descent altitude (MDA) is the lowest altitude, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle-to-land maneuvering in execution of a standard instrument approach procedure. The pilot may descend to the MDA, and may maintain it, but must not descend below it until visual reference is obtained, and must initiate a missed approach, if visual reference has not been obtained, on reaching the missed approach point (MAP).