ashtech DG14, Reference Manual

Page: 79 / 390

Differential Operation 59
Differential Operation
The receiver is set as a base station which transmits RTCM message type 1
every second. Following a power cycle it automatically starts transmitting
these corrections again (because you have saved the settings with the
$PASHS,SAV,Y command). To change the message rate, use the
$PASHS,RTC,TYP command.
Moving Base Operation
The DG16 will function as a moving base station. In Differential Base mode,
the DG16 can continuously input real-time reference position updates (at a
rate of 1Hz or less) to the operating remote station using
$PASHS,POS
command. The DG16 remote station accepts and utilizes the entered
reference position in less than 100ms. The remote receiver must receive
continuously transmitted corrections to update the reference position.
Advanced Settings for Differential Base Stations
There are many parameters that control the operation of the receiver. Most
should be left at default values, except for the settings identified in Table 4.2.
Antenna
Locate the antenna with a clear view of the sky.
The antenna position, entered with the
$PASHS,POS command, is the WGS-
84 phase center of the antenna. If you do not have a surveyed position on
which to locate your antenna you may use the command
$PASHS,POS,CUR .
This sets the base station position to the autonomous position calculated by
the receiver. The relative accuracy of the remote receiver positions is the
same, with respect to the base station, as if you had entered the true position
of the antenna. The absolute accuracy translates by the difference between
the nominal base station position (from
$PASHS,POS,CUR ) and the true
WGS-84 position. That is, if the nominal base station position is one meter
north of the true position, then all remote positions are translated north by
exactly one meter. You may check which position was set by using the
$PASHS,RTC,SPD,9 Set internal bit-rate for corrections to burst
mode. Only use the Burst mode with Types
18 and 19.
$PASHS,LPS,1,1,1 Set loop setting for stationary receiver.
$PASHS,SAV,Y Save settings
Table 4.2. Differential Base Station Commands (Continued)
Command Description