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5-2 Acutime 2000 Synchronization Kit User Guide
System Operation
5
5.2 Automatic Operation
When the Acutime 2000 has acquired and locked onto a set of
satellites that pass the mask criteria listed below, and has obtained a
valid ephemeris for each satellite, it performs a self-survey. After a
number of position fixes, lasting approximately 40 minutes, the self-
survey is complete. At that time, the Acutime 2000 automatically
switches to a time-only mode and periodic outputs of navigation
information cease.
5.2.1 Satellite Masks
The Acutime 2000 continuously tracks and uses up to eight satellites
in an overdetermined clock solution. The satellites must pass the
mask criteria to be included in the solution.
Table 5-1 lists the default satellite masks used by the Acutime 2000.
These masks serve as the screening criteria for satellites used in fix
computations and ensure that solutions meet a minimum level of
accuracy. The satellite masks can be adjusted using the TSIP protocol
described in Appendix A, Trimble Standard Interface Protocol.
Elevation Mask
Satellites below 10° elevation are not used in the solution. Generally,
signals from low-elevation satellites are of poorer quality than signals
from higher elevation satellites. These signals travel farther through
the ionospheric and tropospheric layers and undergo distortion due to
these atmospheric conditions.
Table 5-1 Default Satellite Mask Settings
Mask Setting Notes
Elevation 10° SV elevation above horizon
SNR 4 Signal strength
DOP 8 Self-survey only