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Pilot/Controller Glossary 

6/17/21 

GNSS [ICAO]

 

(See 

GLOBAL NAVIGATION SATELLITE 

SYSTEM

.) 

GNSS MEA

 

(See GLOBAL NAVIGATION SATELLITE 

SYSTEM MINIMUM EN ROUTE IFR 
ALTITUDE.) 

GO AHEAD

 Proceed with your message. Not to be 

used for any other purpose. 

GO AROUND

 Instructions for a pilot to abandon 

his/her approach to landing. Additional instructions 
may follow. Unless otherwise advised by ATC, a 
VFR aircraft or an aircraft conducting visual 
approach should overfly the runway while climbing 
to traffic pattern altitude and enter the traffic pattern 
via the crosswind leg. A pilot on an IFR flight plan 
making an instrument approach should execute the 
published missed approach procedure or proceed as 
instructed by ATC; e.g., “Go around” (additional 
instructions if required). 

(See LOW APPROACH.) 
(See MISSED APPROACH.) 

GPD

 

(See GRAPHIC PLAN DISPLAY.) 

GPS

 

(See GLOBAL POSITIONING SYSTEM.) 

GRAPHIC PLAN DISPLAY (GPD)

 A view 

available with EDST that provides a graphic display 
of aircraft, traffic, and notification of predicted 
conflicts. Graphic routes for Current Plans and Trial 
Plans are displayed upon controller request. 

(See 

EN ROUTE DECISION SUPPORT TOOL.

GROSS NAVIGATION ERROR (GNE) 

 A lateral 

deviation of 10 NM or more from the aircraft’s 
cleared route. 

GROUND BASED AUGMENTATION SYSTEM 
(GBAS)– A ground based GNSS station which 
provides local differential corrections, integrity 
parameters and approach data via VHF data broadcast 
to GNSS users to meet real-time performance 
requirements for CAT I precision approaches. The 
aircraft applies the broadcast data to improve the 
accuracy and integrity of its GNSS signals and 
computes the deviations to the selected approach.  A 
single ground station can serve multiple runway ends 
up to an approximate radius of 23 NM. 

GROUND BASED AUGMENTATION SYSTEM 
(GBAS) LANDING SYSTEM (GLS)- A type of 
precision IAP based on local augmentation of GNSS 
data using a single GBAS station to transmit locally 
corrected GNSS data, integrity parameters and 
approach information. This improves the accuracy of 
aircraft GNSS receivers’ signal in space, enabling the 
pilot to fly a precision approach with much greater 
flexibility, reliability and complexity. The GLS 
procedure is published on standard IAP charts, 
features the title GLS with the designated runway and 
minima as low as 200 feet DA. Future plans are 
expected to support Cat II and CAT III operations. 

GROUND CLUTTER

 A pattern produced on the 

radar scope by ground returns which may degrade 
other radar returns in the affected area. The effect of 
ground clutter is minimized by the use of moving 
target indicator (MTI) circuits in the radar equipment 
resulting in a radar presentation which displays only 
targets which are in motion. 

(See CLUTTER.) 

GROUND COMMUNICATION OUTLET (GCO)

 

An unstaffed, remotely controlled, ground/ground 
communications facility. Pilots at uncontrolled 
airports may contact ATC and FSS via VHF radio to 
a telephone connection. If the connection goes to 
ATC, the pilot can obtain an IFR clearance or close 
an IFR flight plan. If the connection goes to Flight 
Service, the pilot can open or close a VFR flight plan; 
obtain an updated weather briefing prior to takeoff; 
close an IFR flight plan; or, for Alaska or MEDEVAC 
only, obtain an IFR clearance. Pilots will use four 
“key clicks” on the VHF radio to contact the 
appropriate ATC facility or six “key clicks” to contact 
the FSS. The GCO system is intended to be used only 
on the ground. 

GROUND CONTROLLED APPROACH

 A radar 

approach system operated from the ground by air 
traffic control personnel transmitting instructions to 
the pilot by radio. The approach may be conducted 
with surveillance radar (ASR) only or with both 
surveillance and precision approach radar (PAR). 
Usage of the term “GCA” by pilots is discouraged 
except when referring to a GCA facility. Pilots should 
specifically request a “PAR” approach when a 
precision radar approach is desired or request an 
“ASR” or “surveillance” approach when a nonpreci-
sion radar approach is desired. 

(See RADAR APPROACH.) 

PCG G