GNSS reception may be displayed as cyclic in nature. A cyclic 12 hour pattern of decreased
GNSS reception typically indicates that the GNSS antenna has an obstructed view of the
horizon. The GNSS satellites are in a 12-hour orbit, so if part of the sky is blocked by large
obstructions, at the same time every day (at approximately 12 hour intervals), the GNSS
reception may be reduced or may vanish altogether. If this occurs, the antenna should be
relocated to afford it an unobstructed view of the sky.
Every hour (displayed in the log as UTC time), VersaSync counts the total number of satel-
lites that were tracked during that hour. The GNSS qualification log shows the number of
satellites that were tracked followed by the number of seconds that the particular number
of satellites were tracked during the hour (3600 seconds indicates a full hour). The num-
ber to the left of the “=” sign indicates the number of satellites tracked and the number to
the right of the “=” sign indicates the number of seconds (out of a total of 3600 seconds in
an hour) that the unit was tracking that number of satellites. For example, “0=3600” indic-
ates the unit was tracking 0 satellites for the entire hour, while “0=2700 1=900” indicates
the unit was tracking one satellite for 900 seconds, but for the remaining portion of the
hour it was tracking zero satellites.
Every hourly entry in the log also contains a quality value, represented by “Q= xxxx”
(where x can be any number from 0000 through 3600). The Qualification log records how
many satellites were tracked over a given hour. If for every second of the hour a tracked
satellite was in view, the Quality value will equal 3600. For every second VersaSync
tracked less than the minimum number of satellites, the value will be less than 3600. The
minimum requirement is one satellite at all times after the unit has completed the GNSS
survey and indicates “Stationary”. A minimum of four satellites are required in order for the
GNSS survey to be initially completed.
If all entries in the qualification log are displayed as “0=3600”, a constant GNSS reception
problem exists, so the cause of the reception issue is continuous. If the unit occasionally
shows 0=3600 but at other times shows that 1 through 12 have numbers of other than
“0000”, the reception is intermittent, so the cause of the reception issue is intermittent. If
the Quality value normally equals 3600 but drops to lower than 3600 about every 12
hours, the issue is likely caused by the GNSS antenna having an obstructed view of the sky.
E x a m p l e G P S Q u a l i f i c a t i o n L o g E n t r y :
6 = 151 7 = 1894 8 = 480 9 = 534 10 = 433 12 = 108 Q = 3600
In this example, VersaSync tracked no less that 6 satellites for the entire hour. Out of the
entire hour, it was tracking 6 satellites for a cumulative total of 151 seconds (not necessarily
in a row). For the duration of the hour, it was tracking, 7, 8, 9, 10 and 12 satellites for a
period of time. Because it was tracking at least at least one satellite for the entire hour, this
Quality value is Q=3600.
246
CHAPTER 4 • VersaSync User Manual Rev. 7.0
4.6 Quality Management
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