Specifications

32 Z-Family Technical Reference Manual
and 22 every minute. Following a power cycle it automatically starts transmitting
these messages again (because you have saved the settings with the $PASHS,SAV,Y
command). You can also set up the Base Station to use messages 20 & 21 instead of
18 & 19. You can not use DBN and RTCM messages on the same serial port. You can
generate DBN from one port while generating RTCM from a different port.
Advanced Base Station Operation
Recommended Advanced Parameter Settings for 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 3.1 through Table 3.5.
Antenna
Locate the antenna with a clear view of the sky.
The antenna position, entered with the $PASHS,POS command, is the WGS84 phase
center of the antenna if the antenna reduction mode (ANR) is OFF. It is the ground
mark position if ANR is ON (or CPD if the receiver is set as CPD base). Do not use
ANR = CPD when setting up a combined Differential and RTK base since the
position entered is interpreted differently (for more information, see "Antenna
Reduction" on page 24). If you do not have a surveyed position on which to locate
your antenna you may use the command $PASHS,CPD,ENT along with Ashtech
DBN messages. 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,CPD,ENT) and the true WGS84 position. That is, if
the nominal base station position is one meter north of the true position, then all
remote positions will be translated north by exactly one meter.
Message Rate
To improve Differential and RTK performance, minimize base station data latency by
using the highest possible data rates that your data link supports. There are three
different settings that affect data rates:
• RTCM message bit rate. $PASHS,RTC,SPD. This is the internal bit rate
used to generate the RTCM messages. This should be as high as possible
without exceeding the baud rate of the serial port. Recommended bit rate