YSI SonTek RiverSurveyor, Системное руководство

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SonTek/YSI Inc
RiverSurveyor System Manual (May 1, 2007)
145
•
Watch for significant pitch and roll that may cause a transducer to come out of the water.
Try to avoid conditions where the boat is exposed to significant rotations.
•
Clear any debris that may have been caught or wrapped around the transducer head.
•
Select a different section for the measurement.
•
Use seeding material in the water. This may be difficult for long transects or in deep water.
The profile extrapolation graph shows flow traveling in opposite directions.
The site you are using may be experiencing stratified or bi-directional flow.
•
These flow conditions may be present in the area you are conducting your measurements.
Typically these conditions occur in areas of tidal influence. See §
4.3.4
–
Stratified Flows
.
The extrapolated profile does not match the measured velocities.
The velocity profile extrapolation parameters may be incorrect.
•
Check the parameters that you have set in the
Velocity Profile Extrapolation
dialog box
(§
5.2
), especially the method and values for have selected in the
Discard Data
field.
9.8. DQI Window Conditions
My DQI value is very high.
The water is very shallow and therefore only a few cells of velocity data can be measured.
The measured current velocities are experiencing high standard deviations.
Bottom-track has been lost.
•
Bottom-track has been lost (see §
9.2
).
•
GPS or Echo Sounder communication has been lost (see §
9.3
and §
9.4
).
•
If possible, reduce cell size in
User Setup
dialog box (§
7.3.4
) so more cells are measured.
•
Reduce vessel speed.
•
In some cases, high DQI values may be unavoidable. This typically happens in very shallow
water or when you approach the minimum depth for your system’s frequency (
Table 3-1
).
There are several spikes in the DQI data.
You may have lost bottom-track several times while crossing the transect.
The water depth varies dramatically across the transect.
•
If possible, reduce cell size in
User Setup
dialog box (§
7.3.4
) so more cells are measured.
•
Reduce vessel speed and try to keep a constant speed.
•
In some cases, high DQI values may be unavoidable. This typically happens in very shallow
water or when you approach the minimum depth for your system’s frequency (
Table 3-1
).
•
Select a different measurement site.
9.9. Discharge Calculation Conditions
Multiple discharge calculations across the same transect do not match.
Flow conditions may have changed since you completed the last transect. This may be the case
in areas of high tidal variation or when the measurement section is downstream of a man-made
structure that regularly alters the flow conditions.