Definition
A precision approach and landing system that uses satellite-based navigation, augmented by a ground station near the airport, to provide lateral and vertical guidance to a runway. The ground station broadcasts correction data and approach path information by VHF data link to a suitably equipped aircraft, allowing approach minimums comparable to an ILS.
Plain English
A landing guidance system that uses GPS signals, sharpened up by a small ground station at the airport, to guide an aircraft down to the runway with both side-to-side and up-and-down accuracy.
Context Anchor
Seen on instrument approach charts and in landing minimums when a runway has a GLS approach available.
Derivation
Built from 'Global Navigation Satellite System' (GNSS) — the worldwide network of navigation satellites — plus 'Landing System.' The name signals that it does the same job as an ILS, but using satellites instead of ground-based radio beams.
Why Pilots Care
It allows precision approaches at airports that lack traditional ground-based systems, often permitting lower landing minimums and greater access.
Intuition Check
GLS does not mean the satellites land the airplane. It means the airplane uses corrected satellite position information to follow published guidance toward the runway.
Example Sentence 1
The crew briefed the GLS approach to runway 28, noting the minimums were similar to the ILS for the same runway.
Example Sentence 2
With GLS available, the airport could accept arrivals in weather that would otherwise require a circling approach.