Specifications

Operation 17
Operation
receivers are moving together, their position measurements would be different,
because each receiver will report a position for a snapshot taken at a different time.
Fortunately, if a receiver obtains measurements from four or more satellites it can
determine its own internal clock error. In order to reduce the effects mentioned
previously, most receivers use the computed clock error to periodically reset the
internal receiver clock to remain close to GPS system time (within a millisecond).
This method does not entirely remove the effects mentioned above and furthermore
causes jumps in the raw measurements obtained by the receiver; all of which the user
must account for when processing the data.
The receiver offers a GPS Time Sync Mode, which almost completely removes the
effects of the receiver clock error. For example, the jumps in the raw measurements
do not appear in GPS Time Sync Mode, and also in zero baseline tests, two Ashtech
receivers in GPS Time Sync Mode will provide very closely matching pseudo-range
measurements.
Default Parameters
During the normal course of receiver operation, a typical user will often change one
or more receiver parameters such as recording interval, port baud rate, or elevation
mask. To save new settings, the user must save the current setting to memory or else
all parameters (with a few exceptions) will be reset to the default values during a
power cycle. The exceptions are session programming parameters, modem setting
parameters, MET (meteorological) and TLT (tilt) parameters, and the POW (power)
parameters. Saving parameters to memory can be done in two ways; either by
enabling the SAVE option in the SETTINGS menu of the LED interface (only for the
Z-Surveyor and Z-FX), or by issuing a $PASHS,SAV,Y command to the serial port.
When parameters are saved to the memory, they are maintained until a memory reset
or a receiver initialization is performed which will reset all parameters back to their
default.
Only the parameters modified prior to issuing the SAV command are saved in memory. Any
parameter modified after SAV is issued reverts to default after power cycle.
The following table lists the default values of all user parameters.
Table 2.4: Default Values
Parameter Description Default
SVS Satellite Tracking Selection Y for all
PMD Position Mode Selection 0