Receiver Overview - Topcon Net-G3A Operator's Manual

Introduction
• Availability – The availability of satellites affects the calculation
of valid positions. The more visible satellites available, the more
valid and accurate the position. Natural and man-made objects
can block, interrupt and distort signals, lowering the number of
available satellites and adversely affecting signal reception.
• Integrity – Fault tolerance allows a position to have greater
integrity, increasing accuracy. Several factors combine to provide
fault tolerance, including:
– Five or more visible satellites for only GPS or only
GLONASS; six or more satellites for mixed scenarios.
– Satellite Based Augmentation Systems (WAAS, EGNOS,
etc.) creates and transmit, along with DGPS corrections, data
integrity information (for example, satellite health warnings).
– Current ephemerides and almanacs.

Receiver Overview

The Net-G3A, with G3 tracking technology, represents the latest in
GNSS-capable technology. This receiver provides greater value by
virtue of its ability to keep up with changes in GNSS-signal
enhancements through simple firmware upgrades, protecting your
investment to the highest possible degree.
When power is turned on and the receiver self-test is completed, the
receiver's 144 channels initialize and begin tracking visible satellites.
Each of the receiver's channels can be used to track any one of the
GPS, GLONASS, or GALILEO signals. The number of channels
available allows the receiver to track all visible GNSS satellites at any
time and location.
An external GNSS antenna equipped with a low noise amplifier
(LNA) and the receiver's radio frequency (RF) device are connected
with a coaxial cable. The wide-band signal received is down-
converted, filtered, digitized, and assigned to different channels. The
receiver processor controls the process of signal tracking.
Once the signal is locked in the channel, it is demodulated and
necessary signal parameters (carrier and code phases) are measured.
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NET-G3A Operator's Manual