Topcon Net-G3A, Руководство оператора

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Introduction
NET-G3A Operator’s Manual
1-4
the minimum number of satellites needed to compute a position is
four. In a mixed satellite scenario (GPS, GLONASS, GALILEO), the
receiver must lock on to five or more satellites to account for the
different time scales used in these systems and to obtain an absolute
position.
Calculating Differential Positions
DGPS, or Differential GPS, is a relative positioning technique where
the measurements from two or more remote receivers are combined
and processed using sophisticated algorithms to calculate the
receivers’ relative coordinates with high accuracy.
DGPS accommodates various implementation techniques that can be
classified according to the following criteria:
• The type of GNSS measurements used, either code-phase
differential measurements or carrier-phase differential
measurements.
• If real-time or post-mission results are required, then real-time
applications can be further divided according to the source of
differential data and the communication link used.
With DGPS in its most traditional approach, one receiver is placed at
a known, surveyed location and is referred to as the reference receiver
or base station. Another receiver is placed at an unknown location and
is referred to as the remote receiver or rover receiver. The reference
station collects the code-phase and carrier-phase measurements from
each GNSS satellite in view.
• For real-time applications, these measurements and the reference
station coordinates are then built up to the industry standard
RTCM—or various proprietary standards established for
transmitting differential data—and broadcast to the remote
receiver(s) using a data communication link. The remote receiver
applies the transmitted measurement information to its observed
measurements of the same satellites.
• For post-mission applications, the simultaneous measurements
from reference and remote stations are normally recorded to the
receiver’s internal memory (not sent over communication link).
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