ashtech DG14, Reference Manual

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Basic Operation 29
This chapter covers a variety of DG16 operating parameters and options,
including system setup, power-up, command format, serial port configuration,
receiver settings and status, the satellite search algorithm, position modes,
altitude hold definition, the ionospheric model, NMEA outputs, raw data outputs,
differential operation, the photogrammetry option, the pulse-per-second option,
and other options.
The DG16’s three RS-232 ports (ports A, B, and the optional port C) can receive
command messages from an external control device, send response messages to
an external control device (such as a PC), output data to a separate data logging
device, and send or receive differential corrections from a reference or remote
station.
DG16 Input Messages
Input messages are comprised of set command messages, query command
messages, and general command messages. These messages comply with the
format defined in the NMEA 0183 standard to the following extent:
• NMEA 0183 ASCII byte strings following a dollar sign ($) character
• Data fields are separated by commas
• Checksum character delimiter and NMEA checksum bytes are recognized
by the DG16 but are optional. The hexadecimal checksum is computed by