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5700 GPS Receiver User Guide 93
Real-Time Kinematic (RTK) Surveying 8
Applications
8.2.3 Data Link
The data link transfers the reference receiver’s carrier phase and code
measurements, and the location and description of the reference
station, to the rover.
The TRIMMARK 3 reference radio modem, with the 5700 receiver’s
internal receive-only radio, is designed for 5700 receiver RTK
operation. TRIMTALK 450 radio modems are also customized for
RTK applications. You can also use third-party radio modems, cellular
phones, or satellite communication links to transmit reference station
data to one or more rover sites.
Factors to consider when choosing a data link include:
• Throughput capacity
•Range
• Duty cycle
• Error checking and correction
• Power consumption
The data link must support at least 2400 baud throughput. However, a
throughput of 9600 baud is preferable.
Correction message formats
In addition to selecting a data link, you need to decide in which format
messages will be transmitted over the data link. The 5700 receiver
supports two standards for RTK positioning: the Compact
Measurement Record (CMR) format and the RTCM/RTK message
format.
The Compact Measurement Record (CMR) format was designed by
Trimble and is supported by all Trimble RTK products. CMR
messages require at least a 2400 baud data link.