Trimble GNSS receivers use Version 2 protocol for single-frequency DGPS type
corrections. Carrier phase corrections are available on Version 2, or on the
newer Version 3 RTCM protocol, which is available on certain Trimble dual-
frequency receivers. The Version 3 RTCM protocol is more compact but is not as
widely supported as Version 2.
RTK
real-time kinematic. A real-time differential GPS method that uses carrier
phasemeasurements for greater.
SBAS
Satellite-Based Augmentation System. SBAS is based on differential GPS, but
applies to wide area (WAAS/EGNOS/MSAS) networks of reference stations.
Corrections and additional information are broadcast using geostationary
satellites.
signal-to-noise ratio
SNR. The signal strength of a satellite is a measure of the information content of
the signal, relative to the signal’s noise. The typical SNR of a satellite at 30°
elevation is between 47 and 50 dBHz.
skyplot
The satellite skyplot confirms reception of a differentially corrected GNSS signal
and displays the number of satellites tracked by the GNSS receiver, as well as
their relative positions.
SNR
See signal-to-noise ratio.
Source-table
The NTripCaster maintains a source-table containing information on available
NTripSources, networks of NTripSources, and NTripCasters, to be sent to an
NTripClient on request. Source-table records are dedicated to one of the
following:
l
data STReams (record type STR)
l
CASters (record type CAS)
l
NETworks of data streams (record type NET)
All NTripClients must be able to decode record type STR. Decoding types CAS
and NET is an optional feature. All data fields in the source-table records are
separated using the semicolon character.
triple frequency GPS
A type of receiver that uses three carrier phase measurements (L1, L2, and L5).
UTC
Universal Time Coordinated. A time standard based on local solar mean time at
the Greenwich meridian.
VRS
Virtual Reference Station. A VRS system consists of GNSS hardware, software,
and communication links. It uses data from a network of base stations to provide
corrections to each rover that are more accurate than corrections from a single
base station.
To start using VRS corrections, the rover sends its position to the VRS server. The
VRS server uses the base station data to model systematic errors (such as
ionospheric noise) at the rover position. It then sends RTCM correction
messages back to the rover.
SPS985 GNSS Smart Antenna Getting Started Guide 35
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General