Base Station - ashtech DG16 Reference Manual

3, 6, 9, and 16, listed in Table 4.1:
The DG16 uses the six-of-eight format (data bits a1 through a6 of an eight-bit
byte) for differential corrections.
When the RTCM remote option [U] is installed and the DG16 is set in
differential remote mode, it can decode RTCM message types 1, 2, 3, 6, 9,
and 16, but uses only types 1, 2, and 9 to correct its position calculations.
When using radio-modems for the communication link, the DG16 in remote
mode is able to recover bit slippage.
You can configure the DG16 as an RTCM Base (Reference) Station, and can
enable or disable differential-correction message output from the receiver.
When enabled, the DG16 sends message types 1, 2, and 9 continuously and
can send either type 3 or type 16 individually. If type 1 or type 9 messages
have been enabled and the ephemeris changes in one or more satellites, the
base station automatically generates a type 2 message with the delta IODE
information. This automatic type 2 message generates independently of the
setting for type 2 messages.
For all messages, you can set the period and internal bit rate of correction
transmission using the $PASHS,RTC,TYP and $PASHS,RTC,SPD
commands. You can control the delay for switching to the new IODE using
the $PASHS,RTC,IOD command.
The DG16 computes differential corrections for up to 12 GPS satellites, can
compute differential corrections for up to two SBAS satellites, and can make
use of SBAS integrity information. The DG16 can also output corrections
based on a combination of GPS satellites, SBAS satellites, and/or beacon
56
Table 4.1. RTCM Format
Message
Contents of message
Type
1 Differential GPS corrections
2 Delta differential corrections
3 Reference station coordinates
6 Null frame
9 High-rate differential GPS corrections
16 Special Message
DG14 and DG16 Board & Sensor Reference Manual