Abbreviations
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Trm
Transmitter
TRU
Transmit/receive unit
TSA
Time of shortest approach
TSS
Traffic separation schemes
tt&c
Telemetry tracking & command
TU
Terminal unit
UAIS
Universal Automatic Identification System
UAV
Unmanned aerial vehicle
UF
Uncertainty function
UHF
Ultra-high frequency
UHFG
Ultra-high-frequency generator
ULS
Uplink station
UMAS
Unified Measurement Acquisition Stations
USNO
United States Marine Observatory
UTC
Universal Time Coordinated
VCO
Voltage-controlled oscillator
VDF
VHF direction finder
VDOP
Vertical dilution of precision
vessel POB Vessel persons onboard
VHF
Very high frequency
VOR
Very-high-frequency omnidirectional range
VP
Vertical plane
VRC
Variable range circle
VTMS
Vessel traffic management system
WAAS
Wide Area Augmentation System
WDCMS
Wide-area differential correction and monitoring system
WNRS
Weather-navigational radar station
WP
Waypoints
WRS
Wide-area reference stations
WS
Wind shear