Topcon HiPer Ga, Operator'S Manual

Page: 19 / 162

Principles of Operation
P/N 7010-0816
1-5
The real-time kinematic (RTK) method is the most precise method of
real-time surveying. RTK requires at least two receivers collecting
navigation data and communication data link between the receivers.
One of the receivers is usually at a known location (Base) and the
other is at an unknown location (Rover). The Base receiver collects
carrier phase measurements, generates RTK corrections, and sends
this data to the Rover receiver. The Rover processes this transmitted
data with its own carrier phase observations to compute its relative
position with high accuracy, achieving an RTK accuracy of up to 1 cm
horizontal and 1.5 cm vertical.
Essential Components for Quality Surveying
Achieving quality position results requires the following elements:
• Accuracy – The accuracy of a position primarily depends upon
the satellite geometry (Geometric Dilution of Precision, or
GDOP) and the measurement (ranging) errors.
– Differential positioning (DGPS and RTK) strongly mitigates
atmospheric and orbital errors, and counteracts Selective
Availability (SA) signals the US Department of Defense
transmits with GPS signals.
– The more satellites in view, the stronger the signal, the lower
the DOP number, the higher positioning accuracy.
• 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:
– Receiver Autonomous Integrity Monitoring (RAIM) detects
faulty GNSS satellites and removes them from the position
calculation.
– Five or more visible satellites for only GPS or only
GLONASS; six or more satellites for mixed scenarios.