Pilot/Controller Glossary

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 from a cleared track, normally in excess of
25 Nautical Miles (NM). More stringent standards
(for example, 10NM in some parts of the North
Atlantic region) may be used in certain regions to
support reductions in lateral separation.
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
minims low as 200 feet DA. Future plans are
expected to support Cat II and CAT III operations.
GROUND-BASED TRANSCEIVER (GBT)- The
ground-based transmitter/receiver (transceiver) receives automatic dependent surveillance-broadcast
messages, which are forwarded to an air traffic
control facility for processing and display with other
radar targets on the plan position indicator (radar
display).
(See AUTOMATIC DEPENDENT
SURVEILLANCE-BROADCAST.)

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 to a
telephone connection to obtain an instrument
clearance or close a VFR or IFR flight plan. They may
also get an updated weather briefing prior to takeoff.
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