NavCom SF-2040 Rev.F - Manual (Page 91)

SF-2040 User Guide – Rev. F
RTCM (Radio Technical Commission for Maritime
Services) a standard format for Differential GPS
corrections used to transmit corrections from a base
station to rovers. RTCM allows both real-time
kinematic (RTK) data collection and post-processed
differential data collection. RTCM SC-104 (RTCM
Special Committee 104) is the most commonly used
version of RTCM message.
RTK see Real-time kinematic.
RTG Real Time GIPSY, a processing technique
developed by NASA’s Jet Propulsion Laboratory to
provide a single set of real time global corrections for
the GPS satellites.
S/A see Selective Availability.
SBAS (Satellite Based Augmentation System) this
is a more general term, which encompasses
StarFire™, WAAS, EGNOS, MSAS, and GAGAN
type corrections.
Selective Availability (S/A) is the deliberate
degradation of the GPS signal by encrypting the P-
code and dithering the satellite clock. When the US
Department of Defense uses S/A, the signal contains
errors, which can cause positions to be inaccurate by
as much as 100 meters.
Signal-to-Noise Ratio (SNR) is a measure of a
satellite’s signal strength.
single-frequency is a type of receiver that only uses
the L1 GPS signal. There is no compensation for
ionospheric effects.
SNR see signal-to-noise Ratio.
StarFire ™ a set of real-time global orbit and clock
corrections for GPS satellites. StarFire
™ equipped
receivers are capable of real-time decimeter
positioning
Glossary-89