transmission. Many manufacturers have incorporated the processor within the GPS receiver, eliminating
the need for an external processing device. The recommended data format is that proposed by the Radio
Technical Commission for Maritime (RTCM) Services Special Committee (SC). The processor should
be capable of computing and formatting PRCs every 1 to 3 seconds.
c. Communication Link. A communication link is used as a transfer media for differential
corrections. The main requirement of the communication link is that the transmission be at a minimum
rate of 300 bits per second. The type of communication system is dependent on the user's requirements.
5-36. Differential Global Positioning System Carrier Phase Horizontal-Positioning Techniques.
Differential GPS carrier phase surveying is used to obtain the highest precision from GPS and has direct
application to most military topographic and engineering surveys. Manufacturers' procedures should be
followed for conducting a GPS field survey. The following six basic DGPS techniques are in use:
Static.
Stop-and-go kinematic.
Kinematic.
Pseudokinematic.
Rapid static.
OTF/RTK.
Project horizontal-control densification can be performed using any one of these techniques.
Procedurally, all six techniques are similar in that each measures a 3D baseline vector between a
receiver at one point (usually of known local-project coordinates) and a second receiver at another point,
resulting in a vector difference between the two occupied points. The major distinction between static
and stop-and-go kinematic baseline measurements is the method by which the carrier-wave integer-cycle
ambiguities are resolved; otherwise, they are functionally the same.
Cycle ambiguity (or integer ambiguity) is the unknown number of whole carrier wavelengths
between the satellite and receiver. Successful ambiguity resolution is required for successful
baseline formulations. In static surveying, instrumental error and ambiguity resolution can
be achieved through long-term averaging and simple geometrical principles, resulting in
solutions to a linear equation that produces a resultant position. Ambiguity resolution can
also be achieved through a combination of the pseudorange and carrier beat measurements,
made possible by knowledge of the PRN modulation code.
5-27
EN0593
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