Definition
The service delivery point (SDP) is a defined three-dimensional point in space, referenced to the WGS-84 datum, used in Required Navigation Performance (RNP) and Localizer Performance with Vertical guidance (LPV) approaches as the reference for the final approach path. The aircraft's vertical guidance is computed relative to this point, which is positioned above the runway threshold to provide the correct glidepath angle and threshold crossing height.
Plain English
It's a fixed point in space, near the runway threshold, that the airplane's GPS-based approach uses as the target for lining up the final descent. The approach guidance is built around getting the aircraft to cross over this point at the right height and angle.
Context Anchor
You are most likely to see SDP in FAA acronym lists, NOTAM-related material, or airport information procedures, not as a normal cockpit callout.
Derivation
From everyday English: the 'point' where the navigation system 'delivers' the 'service' of vertical guidance to the pilot. The name describes its function — it's where the guidance system hands off the aircraft to the runway environment.
Why Pilots Care
On a precision-like GPS approach (LPV or RNP), the glidepath you're flying is geometrically anchored to the SDP. Understanding that the vertical guidance is built around a specific point — not a ground-based signal like an ILS — helps explain why GPS approach minima and threshold crossing heights behave the way they do.
Intuition Check
Do not read “point” as a navigation fix or a spot you fly over. Here it means an approved handoff point in an information system.
Example Sentence 1
On an LPV approach, the glidepath angle is calculated from the service delivery point above the runway threshold.
Example Sentence 2
NOTAM updates are distributed through the designated SDP.