Javad TRIUMPH-1, Operator'S Manual

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Introduction
Principles of Operation
Essential Components for Quality Surveying
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• 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 rover
stations are normally recorded to the receiver’s internal memory (not sent over
communication link). Later, the data are downloaded to computer, combined, and
processed.
Using this technique, the spatially correlated errors – such as satellite orbital errors, ionospheric
errors, and tropospheric errors – can be significantly reduced, thus improving the position
solution accuracy.
A number of differential positioning implementations exist, including post-processing surveying,
real-time kinematic surveying, maritime radio beacons, geostationary satellites, and satellite
based augmentation systems (WAAS, EGNOS, MSAS). 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.
1.1.4. 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.