Leaders in Pipeline Survey Systems
4 - 12
OPERATING MANUAL
4.9 Notes on GPS
GPS is an acronym for Global Positioning System. There are 24 satellites in low-
earth orbit. The GPS receiver in C-SCAN receives data from a number of these
(maximum 12) depending on which satellites are ‘in-view’.
When the GPS unit is first turned on, the GPS unit attempts to acquire the
satellites ‘in-view’. Acquisition times vary from 10 seconds to 45 minutes.
If the detector has been moved a large distance or it is the first time the
detector has been used it is more likely that the acquisition time will be
nearer to 45 minutes. It is important that the detector (with GPS ON) be
switched on for at least 15 minutes after a position is displayed. This will
ensure a fast turn-on next time.
The minimum number of satellites for position is 3. The more satellites that
are acquired, the more accurate the data that is displayed.
It is very important to check whether the position displayed is the current
position. This can be checked by pressing GPS SAT key in the search
screen.
This will show GPS:GOOD SAT:#6 as in the above example.
If GPS:BAD is shown it means that the current position is incorrect, or that the
satellites have not been acquired or have lost acquisition.
If GPS:OLD is shown it means that the data is more than 10 seconds out of date.
As the data is normally updated every 1 second, this could mean that acquisition
is about to be lost.
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