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GPS Acronyms and Abbreviations

Click the arrow Return to the top of the pageto return to the beginning of the Table of Contents.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |

1 PPM - 1 Pulse Per Minute Return to the top of the page

1 PPS - 1 Pulse Per Second
14AF - 14th Air Force, USAF
19 SOPS - 19th Space Operations Squadron, USAF
1-D - One-dimensional
1 SOPS - 1st Space Operations Squadron, USAF
2-D - Two Dimensional
2DRMS - Two times the standard deviation or Twice Distance Root Mean Squared
2 SOPS - 2nd Satellite Operations Squadron, USAF
3-D - Three Dimensional
4-D - Four Dimensional (3-D plus time)

A/C - Aircraft Return to the top of the page
A/D - Analog to Digital
A/J - Anti-Jamming
AAATS - Australian Advanced Air Traffic Services
ABAS - Aircraft-based Augmentation Systems
ABM - Abeam
ACI - Allocated Configuration Identification
ACU - Antenna Control Unit
ACSM - American Congress on Surveying and Mapping
A/D - Analog To Digital
ADC - Analog to digital converter
ADF - Automatic Direction Finder
ADI - Attitude Director lndicator
ADIU - Advanced Digital Interface Unit
ADP - Automated Data Processing
ADR - Accumulated Delta Range
ADS - Automatic Dependent Surveillance
AE - Antenna Electronics
AECB - Atomic Energy Control Board
AF - Air Force
AFB - Air Force Base
AFI - Automatic Fault Indication
AFSPC - Air Force Space Command
AGL - Above Ground Level
AHRS - Attitude Heading Reference System
AI - Artificial Intelligence
AIAA - American Institute of Aeronautics and Astronautics
AIS - Automated Information System
AJ - Antijamming
ALT - Alternate
ALT - Altitude
AM - Amplitude Modulation
AM/FM - Automated Mapping and Facilities Management
AMCS - Alternate Master Control Station
ANE - Autonomous Navigation Emulator
ANSI - American National Standards Institute
ANTB - Advanced Navigation Test Bed
AoA - Analysis of Alternatives
AOA - Airport Operations Area
AOA - Angle-of-Attack
AOC - Aeronautical Operation Control
AOC - Auxiliary Output Chip
AOC - Auxiliary Output Chip
AOCS - Attitude and Orbit Control System
AOM - Aircraft Operating Manual
AOO - Area of Operations
AOPA - Aircraft Owners And Pilots Association
AOR - Area of responsibility
AORP - Airfield Obstruction Reduction Program
AP - Acquisition Plan
APA - Airline Pilots Association
APMS - Automated Performance Measurement System
APPR - Approach/Approach Mode
APPS - Analytical Photogrammetric Positioning System
APR - April
APU - Auxiliary Power Unit
AQP - Advanced Qualification Program
ARGO - Automatic Ranging Grid Overlay
ARNS - Aeronautical Radio Navigation Service
ARPA - Advanced Research Projects Agency
ARR - Arrival
ARTCC - Air Route Traffic Control Center
ARTS - Automated Remote Tracking Station
ARTS - Automated Radar Terminal System
AS - AntiSpoofing
ASCII - American Standard Code for Interface and Interchange
ASF - Additional Secondary Factor (Loran-C)
ASI - Air Speed Indicator
ASIC - Application Specific Integrated Circuit
ASPRS - American Society of Photogrammetry and Remote Sensing
ASR - Airport Surveillance Radar
ATA - Air Transport Association
ATC - Air Traffic Control
ATCS - Advanced Train Control Systems
ATCSCC - Air Traffic Control System Command Center
ATE - Automatic Test Equipment
ATM - Air Transportation Management
ATON - Aids To Navigation
ATS - Automatic Throttle System
AUG - August
Autonav - Autonomous Navigation
AVAIL - Available
AVL - Automatic Vehicle Location
AVL - Automatic Vehicle Location -
AVLN - Automatic Vehicle Location And Navigation
AVM - Automatic Vehicle Monitoring
AWACS - Airborne Warning And Control System
AWAS - Automated Weather Advisory Station
AWIPS - Advanced Weather Interactive Processing System

B - Billion Return to the top of the page
BBS - Bulletin Board Service
BCD - Binary Code Decimal
BER - Bit Error Rate
BIPM - International Bureau of Weights and Measures
BITE - Built-in Test Equipment
BMCS - Backup Master Control Station (MCS)
Bps - Bits per second
BPSK - Binary Phase Shift Keying
BRG - Bearing
BRT - Brightness
BUMCS - Back-up Master Control Station

C - Centigrade Return to the top of the page
C&A - Certification and Accreditation
C/A - Coarse Acquisition Code
C/No - Carrier to Noise Ratio
C/PD - Cost/Pricing Data
C2 - Command and Control
C3 - Command, Control, and Communications
C3I - Command, Control, Communications, and Intelligence
CAD - Computer Aided Design
CASE - Computer Aided Software Engineering
CAT - Computer Aided Testing
CBD - Commerce Business Daily
CBT - Computer Based Training
CCB - Configuration Control Board
CCW - Continuous carrier wave
CCW - Coded Continuous Wave
CCZ - Coastal And Confluence Zone
CDMA - Code Division Multiple Access
CDU - Control Display Unit
CDMA - Code Division Multiple Access (GPS)
CEP - Circular error probable
CG - Center of Gravity
CGS - Centimeter-gram-second
CGSIC - Civil Global Positioning System Service Interface Committee
Cl - Cost Index
CLR - Clear
cm - Centimeter
CM - Configuration Management
CMG - Command Managers Guide
CMOS - Complementary Metal Oxide Semiconductor
CMC - Central Maintenance Computer
CMP - Configuration Management Plan
CMS - Command Management Seminar
CNA - Computer Network Attack
CNS - Communications, Navigation, And Surveillance
CO - Contracting Officer; Change Order; Commanding Officer; Colorado
COE - Common Operating Environment; Center of Expertise
CONOPS - Concept of Operations
COP - Circle Of Position
CONUS - Continental United States
CORS - Continuously Operating Reference Station
COTS - Commercial Off-The-Shelf
CPU - Central Processing Unit
CRPA - Controlled Radiation Pattern Antenna
CRT - Cathode Ray Tube
CRYPTO - cryptographic
CS - Control Segment
CTR - Center
CSAT - Constellation System Assessment Team
CTRL - Control
CTS - Colorado Tracking Station
CUE - Common User Element
CVNS - carrier navigation systems
CW - Continuous Wave
CY - Calendar Year

D/A - Digital To Analog Return to the top of the page
D/D - Drift Down
DAC - Digital to Analog Converter
DATALINK - Digitized Information Transfer (air/ground)
dB - Decibel (X = 10 Log X dB)
DBS - Direct Broadcast Satellite
dBW - decibels per watt
DC - Direct Current Electricity
DEC - December
DECR - Decrement
DEG - degree
DEL - Delete
DEP - Departure
DEV - Deviation
DF - direction finding
DGIC - Differential GPS Integrity Channel
DGNS - Doppler GPS Navigation System
DGPS - Differential Global Positioning System
DH - Decision Height
DID - Data Item Description
DIS - Distance
DISCR - Discrepancy
DIST - Distance
DLL - Delay Lock Loop
DLM - Data Loader Module
DLR - Data Loader Receptable
DLS - Data Loader System
DLT - Data Link Terminal
DMA - Defense Mapping Agency
DME - Distance Measuring Equipment
DMU - Data Management Unit
DoD - Department Of Defense
DOE - Department of Energy
DOP - Dilution Of Precision
DoT - Department Of Transportation
DR - Dead Reckoning
DRMS - Distance Root Mean Square
DRS - Dead Reckoning System
DRU - Data Retrival Unit
DT&E - Development Test and Evaluation
DTG - Distance-to-go

E - East Return to the top of the page
EA - Electronic Attack; Evolutionary Acquisition
ECDIS - Electronic Chart Display And Information System
ECEF - Earth Centered, Earth Fixed
EDM - Electronic Distance Measurement
EGNOS - European Geostationary Navigation Overlay Service
EOS - Earth Orbiting System
EPROM - Erasable Programmable Read-Only Memory
EHF - Extremely High Frequency
ETA - Estimated Time Of Arrival
ECE - Earth-Centered-Earth-Fixed
ECEF - Earth Centered, Earth Fixed
ECM - Electronic Countermeasures
ECP - Engineering Change Proposal
ECS - Environmental Control System
EDM - Electronic Distance Measurement
EFIS - Electronic Flight Instrument System
EHF - Extremely High Frequency
EHSI - Electronic Horizontal Situation Indicator
EIU - Electronic Interface Unit
EKMS - Electronic Key Management System
ELEV - Elevation
ELT - Emergency Locator Transmitter
EM - Electro Magnetic
EMC - Electromagnetic Compatibility
EMCON - Emission Control
EMI - Electromagnetic Interference
EMP - Electromagnetic Pulse
EMS - Emergency Medical Services
ENG - Engine
EOL - End of Life
EOW - End of Week
EPR - Engine Pressure Ratio
EPROM - Erasable Programmable Read-Only Memory
EPS - Electric Power System
ES - Electronic Support
ESGN - Electrically Suspended Gyro Navigator
ESM - Electronic Support Measures
EST - Estimated
ETA - Estimated Time of Arrival
ETX - End of Transmission
EU - European Union
EW - Electronic Warfare
EXEC - Execute
Exp - Exponential Function

F - Fahrenheit Return to the top of the page

FAA - Federal Aviation Administration
FAATC - FAA Technical Center - Atlantic City, New Jersey
FADEC - Full Authority Digital Engine Control
FANS - Future Air Navigation Systems
FAR - Federal Acquisition Regulation
FBO - Fixed Based Operator
FCC - Federal Communications Commission
FCC - Flight Control Computer
FCMDR - Flight Commander
FCU - Flight Control Unit
FD - Fault Detection
FDE - Fault Detection Equipment; Fault Detection and Exclusions
FDMA - Frequency Division Multiple Access -
FDR - Flight Data Recorder
FEB - February
FHWA - Federal Highway Administration
FLT - Flight
FI - Fault Isolation
FL - Florida
FM - Frequency Modulation
FMEA Failure Mode and Effects Analysis
FMS - Flight Management Systems
FO - First officer
FOC - Full Operational Capability
FOM - - Figure Of Merit
FOIA - Freedom of Information Act
FOUO - For Official Use Only
FPA - Focal Plane Array
FPM - Feet Per Minute
FQIS - Fuel Quantity Indicating System
FR - From
FRA - Federal Railroad Administration
FRA - Flap Retraction Altitude
FREQ - Frequency
FRP - Federal Radionavigation Plan
FRPA - Fixed Radiation Pattern Antenna
FRPA-GP - FRPA Ground Plane
FSS - Federal Supply Schedule
FT - Feet
FY - fiscal year

GA - General Aviation Return to the top of the page
GA - Ground Antenna
GANS - global access, navigation and safety
GAO - General Accounting Office
GATM - Global Air Traffic Management
GBAS - Ground-based augmentation system
Gbps - Gigabits per second
GDOP - Geometric Dilution Of Precision
GEO - Geosynchronous Earth Orbit
GEOREF - World Geographic Reference System
GHz - Gigahertz
GIAC - GPS Interagency Advisory Council
GIB - GPS Integrity Broadcast
GIC - GPS Integrity Channel
GIS - Geographic Information Systems
GLONASS - Global Navigation Satellite System
GMT - Greenwich Mean Time
GNSS - Global Navigation Satellite Systems
GPS - Global Positioning System
GPSE - GPS Enhancement
GPSIC - GPS Information Center
GRAS - Ground-based regional augmentation system
GRP - Geographical Reference Points
GRS - Geodetic Reference System
GS - Glide Slope
GS - Ground Speed
GSA - General Services Administration
GW - Gross Weight
GYRO - gyroscope

HADGPS - High Accuracy DGPS Return to the top of the page
HANU - High Accuracy Navigational Users
HD - High dynamic
HDG - Heading
HDG - SEL - Heading Select
HDOP - Horizontal Dilution of Precision
HF - High Frequency
HHA - Harbor And Harbor Approach
HF - high frequency
HIRS - High-Resolution Infrared Sounder
HMI - Hazardously Misleading Information
HR - relative height
HUD - Head-Up Display
HV - Host Vehicle
Hz - Hertz (cycles per second)

IALA - International Association Of Lighthouse Authorities Return to the top of the page
ICAO - International Civil Aviation Organization
ICD - Interface Control Document
ICS - Interim Control Segment
ID - Identifier
ICWG - Interface Control Working Group
IDD - Interface Design Document
IEEE - Institute Of Electrical And Electronics Engineers
IERS - International Earth Rotation Service
IF - Intermediate Frequency
IFF - Identification Friend or Foe
IFR - Instrument Flight Rules
IF - Intermediate Frequency
IGEB - Interagency GPS Executive Board
IG - Inspector General
IGS - International GNSS Service
ILS - Instrument Landing System
IMO - International Maritime Organization
INFO - Information
IFRB - International Frequency Registration Board
INIT - Initialization
INMARSAT - International Maritime Satellite
INR - Image Navigation and Registration
INS - Inertial Navigation System
INTC - Intercept
IOC - Initial Operational Capability
ION - Institute Of Navigation
IOT&E - Initial Operational Test and Evaluation
IP - Instrumentation Port
IPT - Integrated Product Team
IRD - Interface Requirements Document
IRS - Inertial Reference System
IRT - Independent Review Team
IRU - Inertial Reference Unit
ISA - International Standard Atmosphere
ISO - International Standards Organization
ITP - Integrated Test Plan
ITRF - International Terrestrial Reference Frame
ITS - Intelligent Transportation System
ITU - International Telecommunication Union
IV&V - Independent Verification and Validation
IVHS - Intelligent Vehicle Highway Systems IW Information Warfare

J/S - Jamming to Signal Ration Return to the top of the page
JAN - January
JCS - Joint Chiefs of Staff
JPALS - Joint Precision Approach and Landing System
JPL - Jet Propulsion Laboratory
JPO - Joint Program Office
JROC - Joint Requirements Oversight Council
JSRA - Joint Sponsored Research Agreement
JSST - J oint Space Support Team
JSTARS - Joint Surveillance, Target Attack Radar System
JTF - Joint Task Force
JTIDS - Joint Tactical Information Distribution System
JUL - July
JUN - June

K - Thousand Return to the top of the page
Kbps - Kilo bits per second
KG - Kilogram
kHz - kilohertz
KHz - Kilohertz
km - Kilometer
KT - (kts) - Knots
kW - Kilowatt

L - Link Return to the top of the page
L - Left
L1 - GPS Carrier Frequency, 1575.42 MHz
L2 - GPS Carrier Frequency, 1227.6 MHz
LAAS - Local Area Augmentation System
LAN - Local Area Network
Lat - Latitude
Lat/Lon - Latitude/Longitude
LBS - L Band System
L2C - Civil signal on L2
L2M - Military-code on L2
L5 - Link 5, carrier frequency = 1176.45 MHz
LAAFB - Los Angeles Air Force Base
LAAS - Local Area Augmentation System
LAN - Local Area Network
LAT - latitude
LCD - Liquid Crystal Display
LCN - Local Communications Network.
LED - Light Emitting Diode
LEO - Low Earth Orbit
LEP - Linear Error Probable
LED - Light emitting diodes
LEO - Low Earth Orbit
LEP - linear error probable
LF - low frequency
LFR - Low-frequency Radio Range
LIM - Limit
LIS - Land Information System
LF - Low Frequency
LO - Local Oscillator
LO - Low
LOC - Localizer Beam
Lon - Longitude
LOP - Line Of Position
Loran - Long Range Navigation
LOS - Line Of Sight
LRC - Long Range Cruise
LRU - Line Replaceable Unit

M - Mach Number Return to the top of the page
m - Meter(s)
M - Million
M/S - Meters per Second
MAG - Magnetic
MAINT - Maintenance
MAN - Manual
MAR - March
MAX - Maximum
mB - Millibar
Mbps - Mega bits per second
MC&G - mapping, charting, and geodesy
MCA - Minimum Crossing Altitude
MCDU - Multipurpose Control Display Unit
M-Code - Military Code
MCS - Master Control Station
MCT - Mean Corrective Maintenance Time
MCW - Modulated Continuous Wave
MCW - modulated continuous wave
MD - Maryland
MDL - Multipurpose Data Link
MEL - Minimum Equipment List
MF - Medium Frequency
MGRS - Military Grid Reference System
MHz - Megahertz
MIDAS - Multi-discipline Data Analysis System
mil - unit of angular measurement equal to an angle having a tangent of 0.001
MILSPEC - Military Specifications
MIN - Minimum
MIN - Minutes
MLRS - multiple launch rocket system
MLS - Microwave Landing System
MLV - Medium Launch Vehicle
mm - millimeter
MMD - Mean Mission Duration
MMR - Multi-Mode Receiver
MN - Magnetic North
MNP - Master Navigation Plan
MNS - Mission Need Statement
MOA - Memorandum of Agreement
MOD - Modified/Modification
MODIS - Moderate-resolution Imaging Spectrometer
MOPS - Minimum Operational Performance Standards
MOU - Memorandum of Understanding
MP - Master Plan
MS - Monitor Station
MSAS - MTSAT Augmentation System
MSG - Message
MSK - Minimum Shift Keying
MSS - Mobile Satellite Service
MSL - Mean Sea Level
MTBF - Mean Time Between Failures
MTSAT - Multifunction Transport Satellite
MU - Management Unit
MWP - Meteorological Weather Processor

N - North Return to the top of the page
N/A - Not Applicable
NACA - National Advisory Committee for Aeronautics
NAD - North American Datum -
NADU - Notice Advisory to DGPS Users
NAGU - Notice Advisory to Glonass Users
NANU - Notice Advisory to Navstar Users
NAS - National Aircraft Standard
NAS - National Airspace System
NASA - National Aeronautics and Space Administration
NATCA - National Air Traffic Controllers Association
NATO - North Atlantic Treaty Organization
NAV - Navigation
NAVAID - Navigational Aid
NAV-msg - . - Navigation Message
NAVSTAR - Navigational Satellite Timing and Ranging
Navwar - Navigation Warfare
NCA - National Command Authority
ND - Navigation Display
NDB - Nondirectional Radio Beacon
NDGPS - Nationwide Differential Global Positioning System
NDS Nuclear Detection Subsystem
NESDIS - National Environmental Satellite, Data, and Information Service
NGS - National Geodetic Survey
NIMA - National Imagery and Mapping Agency
NIST - National Institute of Standards and Technology
Nl - Engine Revolutions per Minute (percent)
NLM - Network Loadable Module
NLR - National Research Laboratory (The Netherlands)
NM - Nautical Mile
Nm - Nautical Mile
NMC - National Meteorological Center
NNSS - Navy Navigation Satellite System (Transit)
NOAA - National Oceanic And Atmospheric Administration
NOS - National Ocean Survey
NRL - Naval Research Laboratory
Ns - Nanosecond
NOAA - National Oceanic and Atmospheric Administration
NOCC - National Operations Command Center (FAA)
NORAD - North American Aerospace Defense Command
NOTAM - Notice for Airman
NOV - November
NPA - Non-precision approach
NRL - Naval Research Laboratory
NRP - National Route Program
NS - Nanosecond
NSC - Non-standard C/A code
NSC - National Security Council
NSTC - National Science and Technology Council
NTIS - National Technical Information Service (Department of Commerce)
NTS - Navigation Technology Satellite
NTSB - National Transportation Safety Board
NW - Northwest Airlines
NWS - National Weather Service

OAB - Operational Advisory Broadcasts Return to the top of the page
OATS - Orbit and Attitude Tracking
OBE - Overtaken by Events
OBS - Omni Bearing Select
OCONUS - Outside the CONUS (Continental United States)
OCS - Operational Control Segment
OEM - Original Equipment Manufacturer
OGE - Operational Ground Equipment
OIS - Orbital Insertion System
OJT - On-the-Job Training
OMB - Office of Management and Budget
ONC - operational navigation chart
OP - Operational
OPCON - operational control
OPSCAP - Operational Status Capability
OPT - Optimum
ORD - Operational Requirements Document
ORRB - Operational Requirements Review Board
ORWG - Operational Requirements Working Group
OS - Operational Stability
OSCARS - Optimum Satellite Constellation Assessment Report Summary
OSD - Office of the Secretary of Defense

P-Code - Precision/Protected Code Return to the top of the page
PADS - Position Azimuth Determining System
PAFB - Peterson Air Force Base, Colorado Springs, CO
PALS - Precision Approach Landing System
PC - Personal Computer
PDD - Presidential Decision Directive
PDOP - Position Dilution Of Precision
PE - Probable error
PERF - Performance
PHARE - Program for Harmonized ATC Research in Europe
PHIBUF - Performance Buffet Limit
PHMI - Probability of Hazardously Misleading Information
PHINOM - Nominal Bank Angle
PINS - Precise Integrated Navigation System
PLGR - Precise Lightweight GPS Receiver
PMI - Preventative Maintenance Instructions
PMS - Performance Management System
PNT - Position, navigation and time
POC - Point of Contact
POS - Position
POS REF - Position Reference
Pos/Nav - positioning/navigation
PPM - Parts Per Million
PPM - Parts Per Million
PPOS - Present Position
PPS - Precise Positioning Service
PPS - Pulse Per Second
PR - Pseudorange
PREV - Previous
PRN - Pseudo Random Noise
PROM - Programmable Read-Only Memory
PTTI - precise time and time interval
PVT - Position, Velocity and Time
PY - Prior Year

QA - Quality Assurance Return to the top of the page
QC - Quality Control
QTY - Quantity
QUAD - Quadrant

R - Right Return to the top of the page
R&D - Research and Development
RAD - Radial
RAIM - Receiver Autonomous Integrity Monitoring
RAM - Random Access Memory
RAP - Reserve Auxiliary Payload
RCVR - Receiver
RDF - Radio Direction Finder
RDOP - Relative Dilution of Precision
RDSS - Radio Determination Satellite Systems
REF - Reference
RF - Radio Frequency
RFI - Radio Frequency Interference
RINEX - Receiver INdependent EXchange format
RLG - ring laser gyro
RMS - Root Mean Square
RNAV - Area Navigation
RNP - Required Navigation Performance
ROM - Read-Only Memory
ROV - Remotely Operated Vehicle
RTCA - Radio Technical Commission for Aeronautics
RTCA-SC - Radio Technical Comission for Aeronautics, Special Committee
RTCM - Radio Technical Commission for Maritime Services
RTK - Real-Time Kinematic
RSS - Root Sum Square
RTCA - - Radio Technical Commission for Aeronautics
RTCM - Ratio Technical Commission for Maritime Services
RTE - Route
RTS - Remote Tracking Station
RVR - Runway Visual Range

S - South Return to the top of the page
S/A - Selective Availability
SA - Selective Availability
SA - Situation Awareness
SA/A-S - selective availability/anti-spoof
SAASM - Selective Availability and Anti-Spoofing Module
SAFB - Schriever Air Force Base (Colorado)
SAR - Selected Acquisition Report; Subsequent Application Review; Search and Rescue; Safety Assessment Report; Special Access Required
SARPS - Standards and Recommended Practices
SATCOM - Satellite Communications
SATNAV - Satellite Navigation
SBIR - Space Based Infrared System; Small Business Innovation Research Program
SC - Special Committee
SCA - Satellite Control Authority/Architecture
SCAT I - Special Category I
SCATANA - Security Control of Air Traffic and Navigation Aids
SCCB - Software Configuration Control Board
SCI - Sensitive Compartmented Information
SCSS - Satellite Control Simulation System
SDLS - Satellite Data Link Standard
SE - Systems Engineering; Support Equipment
sec - Second(s)
SEL - Selected
SEP - - Spherical Error Probable
SES - Severely Errored Seconds
SF - Sub Frame
SGLS - Space-Ground Link Subsystem
SHF - Super High Frequency
SIGMET - Significant Meteorological Information
SIGSEC - Signal Security
SINS - Shipborne INS
SIS - Signal-In-Space
SKYNET - Skynet Communications Satellite
SLEP - Service Life Extension Program
SLR - Satellite Laser Ranging
SLS - Satellite Launch Squadron
SM - Security Module
SME - Subject Matter Experts
SNAPM - Satellite-Based Navigation Accuracy Performance Model
SNR - Signal To Noise Ratio
SOC - Satellite Operations Center
SOIT - Satellite Operational Implementation Team
SONAR - sound navigation ranging
SOP - Standard Operating Procedure
SOPS - Satellite Operations Squadron
SORD - System of Operational Requirements Document
SP - Space
SPS - Standard Positioning Service
SPU - Spacecraft Processor Unit
SQL - Structured Query Language
SRP - Selected Reference Point
SS - Space Segment
SSG - Senior Steering Group
SSM - Sign Status Matrix
SSN - Space surveillance network
SPS - Standard Positioning Service
STB - System Test Bed
STD - Standard
STS - Space Transportation System
STS - System Telecommunication Simulator, Block IIF
STS/TSM - Satellite Telecommunications Simulator (Block IIF)/Telecom Simulator
SV - Space Vehicle
SVN - Space Vehicle NAVSTAR, Space Vehicle Number
T - Trillion; Time Return to the top of the page
T&E - Test and Evaluation
TACAN - Tactical Air Navigation
TAI - International Atomic Time
TBD - To Be Determined
TCA - Terminal Control Area
TCAS - Traffic Alert & Collision Avoidance System
TD - Time Difference
TDMA - Time Division Multiple Access
TDOP - Time Dilution of Precision
TE - Test Equipment
TEMP - Temperature
THDG - True Heading
TN - True North
TO T - echnical Order
TOA - Time of Arrival
TOD - Time Of Day
TOPEX - The Ocean Topography Experiment
TOT - Total
TQM - Total Quality Management
TRACON - Terminal Radar Approach Control Facility.
TRANS - Transition
TSO - Technical Standard Order

UAV - Unmanned Aerial Vehicle Return to the top of the page
UE - User Equipment
UERE - User Equivalent Range Error
UEE - User Equipment Error
UHF - Ultra High Frequency
UNK - Unknown(s)
URE - User Range Error
US - User Segment
USAF - United States Air Force
USCG - United States Coast Guard
USGIC - US GPS Industry Council
USGS - US Geological Survey
USNO - US Naval Observatory
UT - Universal Time
UTC - Coordinated Universal Time
UTC (USNO) - Coordinated Universal Time as maintained by the USNO

V - Velocity Return to the top of the page
V&V - Verification and Validation
VAR - Variation
VAR - Visual-aural Radio Range
VDOP - Vertical Dilution of Precision
VE - Value Engineering
VFR - Visual Flight Rules
VHF - Very-high Frequency
VLF - very low frequency
VLM - Vehicle Location Monitoring
VMC - Visual Meteorological Conditions
VNAV - Vertical
VOM - Volt-ohm-milliammeter
VOR - very high frequency omnidirectional range station
VOR/DME - Very High Frequency Omnidirectional Range/Distance Measuring Equipment
VORTAC - VHF Omni Range Radio/Tactical Air Navagation
VPATH - Vertical Path
VREF - Reference Velocity
VTC - Vessel Traffic Center
VTOL - Vertical Takeoff and Landing
VTR - Variable Takeoff Rating
VTS - Vessel Traffic Services

W - West Return to the top of the page
WAAS - Wide Area Augmentation System
WADGPS - Wide Area Differential GPS
WAGE - Wide Area GPS Enhancement
WAN - Wide Area Network
Waypoint - Position in space usually on aircraft's flight plan
WGS - World Geodetic System
WGS 84 - World Geodetic System 1984
WPT - Way point
WRC - World Radio Conference
WT - Weight
WWV WWVH - time station call letters
WX - Weather
WXR - Weather Radar

X-BAND - The frequency range between 8000 and 12500 MHz Return to the top of the page
XCVR - Transceiver
XFR - Transfer
XLTR - Translator
XMIT - Transmit
XMITR - Transmitter

Y code - Precise code (GPS) Return to the top of the page
Y2K - Year 2000
YD - Yaw Damper
YSAS - Yaw Stability Augmentation System

Z - Zulu (GMT time) Return to the top of the page