Definition
In the Microwave Landing System (MLS), the approach elevation is the official ground reference point used for vertical guidance on the approach. It is the elevation, measured in feet above mean sea level, at the point where the runway centerline meets the runway threshold. All MLS glidepath calculations are referenced to this point.
Plain English
It is the height above sea level of the spot where the runway begins. The MLS uses this exact spot as its zero point for telling you how high you should be on the way down.
Context Anchor
Seen in MLS instrument approach discussions, especially where the system describes vertical guidance for the final approach to a runway.
Derivation
"Elevation" comes from the Latin elevare, meaning "to lift up." In aviation it specifically means height of a fixed point on the ground above mean sea level — not the height of an aircraft in flight. "Approach" refers to the final segment of flight toward landing. Together: the ground-height reference used for the approach.
Why Pilots Care
It supplies precise vertical guidance that supports safe landings when visibility is low or terrain is challenging.
Grounding Statement
Picture the airplane following a gentle downhill path toward the runway; approach elevation is the MLS guidance that shows whether it is too high, too low, or on that path.
Intuition Check
Do not read approach elevation as the runway’s height above sea level. Here it means vertical approach guidance: the up-and-down path information used while descending to land.
Example Sentence 1
The MLS glidepath angle is measured from the approach elevation at the runway threshold.
Example Sentence 2
Pilots cross-check the approach elevation indicator to confirm they are on the proper glide path before landing.