ashtech DG14, Reference Manual

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Differential Operation 57
Differential Operation
signals.
The DG16 can output differential corrections in either RTCM SC-104 or RTCA
DO-217 format via a serial port. The DG16 uses the six-of-eight format (data
bits a1 through a6 of an eight-bit byte) for communication between the
reference station and user equipment.
RTCM recommends that you use of a highly stable clock with the Type 9 implementation to prevent
degradation of navigation accuracy due to clock drift that can occur between Type 9 messages.
Since the DG16 does not support an external frequency input, be aware of possible degradation in
positioning using Type 9 instead of Type 1 corrections.
Setting Up a Differential Base Station
You must have the Base option [ B ] installed on the receiver.
Figure 4.1 displays a typical DGPS base station configuration.
CAUTION
Errors in the base station reference position will be duplicated in
positions computed by the remote system.