ashtech GG Surveyor, Reference Manual

Page: 39 / 256

Advanced Operation
Advanced Operation 21
Receiver Communications
The built-in command/response firmware allocates the RS-232 ports (A,B, and C) to
receive command messages from an external control device, to send response messages to
a single external control device (such as a PC), to output data to a separate data logging
device, and to send or receive differential corrections from a reference or remote station,
respectively. Messages are summarized in this chapter and covered in detail in Chapter 6,
Command/Response Formats.
Input Messages to the GG Surveyor
The input messages comprise set command messages or query command messages that
either change receiver parameters or request receiver information.
Generally speaking, all set and query commands fall into one of five categories:
• general receiver commands
• NMEA message commands
• raw data commands
• RTCM commands
• CPD (carrier phase differential commands)
All command messages (set or query) can be in upper or lower case followed by <Enter>.
A valid set command, if this command is successfully executed, causes the GG Surveyor
to return the $PASHR,ACK*3D, "acknowledged" response message. Valid query
commands are acknowledged by return of the requested information. A set command
containing a valid $PASHS set command header, followed by character combinations or
parameters unrecognized by the GG Surveyor, returns the $PASHR,NAK*30 "not-
acknowledged" response message. All other invalid commands are ignored.
Output Messages From the GG Surveyor
Output messages are messages the GG Surveyor sends to the data logging device in
response to a set or query command. Output messages comprise general status messages,
command acknowledged/not acknowledged messages, and GPS data messages. The
general status messages are in free-form Ashtech proprietary formats. The command
acknowledged/not acknowledged messages and GPS data messages are in ASCII format
while the raw data messages output in binary format.