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7.2.2 Planning
Carrier Phase Data Collection 7
You require a clear view of the sky at all times when collecting carrier
phase data, so avoid obstacles such as trees, bridges, and tall
buildings. Choose a time of day when you can expect to track a
maximum number of satellites with the best possible geometry.
Note – Always make sure that you collect sufficient useful data while
you are in the field. This is discussed more fully in the following
section.
7.2.3 Collecting Sufficient Data
Always make sure that at least four satellites remain visible for
enough time to provide sufficient useful data for postprocessing.
Number of satellites
To provide sufficient carrier phase data to achieve the required
precision, the Asset Surveyor software needs to log data from at least
four satellites for the minimum time specified. However, you must log
data from at least five satellites for the postprocessing software to
indicate the precision. These five satellites together provide the
necessary redundancy for the precisions required—but you can use
more.
‘Loss of lock’ occurs when the number of available satellites drops
below four. If you minimize the number of times that loss of lock
occurs during the session, you greatly increase the precision of the
postprocessed results.
As you start a session, the Asset Surveyor software starts to record
carrier phase data. As soon as four or more satellites are available, a
counter starts. When the specified Minimum time has elapsed, all of
the carrier phase data recorded during that period can be used during
postprocessing.
TSC1 Asset Surveyor Operation Manual 163