YSI SonTek RiverSurveyor, Системное руководство

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SonTek/YSI Inc
RiverSurveyor System Manual (May 1, 2007)
162
sary, turn off the display of the bottom depth on the Contour Window (
File|Configuration|Show
Bottom Depth on Contour Graph
). Look for insufficient signal-to-noise ratio (3 dB is the recom-
mended minimum). Adjust the SNR threshold (
Processing|SNR Threshold
) as appropriate.
If the echo sounder is available, switch the Depth reference to echo sounder and compare the
depth contour with that from bottom-track. Does the depth contour make sense? Which reference
is more appropriate?
Right click on the x-axis and change the display to Profiles. Look for bad bottom depths (shown
by gray bars at the bottom of the plot) or lost/missing profiles (shown in black). Plotting DQI in
the Data Quality Window can be a good indication of problems.
Change the horizontal display back to Dynamic Distance.
E-3. Step 3 – Check Signal Amplitude Profile Graph
Rewind the measurement (
F9
) and step through each of the profiles using the spacebar.
Watch the depths detected by each of the beams in the
Track Data
tabular display while looking
at the signal amplitudes in the profile graph. Variation in the depths reported by the beams can
be an indicator of a bottom gradient. Typically, on sharp gradients (such as on the edge of a
trapezoidal channel or at a river’s edge) one or two beams will report a significantly different
beam depth to the others. Generally for flat bottoms, the signal responses should be similar in
shape and magnitude for each beam.
Do any of the signal amplitude profiles appear to be consistently or intermittently lower than the
others? This may be an indication of air entrainment or the transducer coming out of the water.
Variation in the shape of the signal may be due to the beams hitting underwater objects such as
large boulders, submerged piling and trees or other vegetation. These objects may not have been
clearly visible during the measurement.
E-4. Step 4 – Tabular Display
The Data Display is the tabular data located on right side of screen. A total of five tables (and the
compass rose) are displayed. The data from this display should be examined thoroughly.
Full forward (
F12
) to the end of the file to display the final accumulated values for each field.
Look at all fields however certain fields have been highlighted for inspection below:
1. Profile Data
•
Profile No.
– The total number of profiles should preferably be more than 40.
•
Elapsed Time
– Elapsed time for the transect should preferably be greater than 2-3 minutes.
2. Discharge Data
•
Meas Q/Est Q
– The % measured discharge should preferably be greater than 50%.
•
Left Q + Right Q
– The discharges on the left and right edges should be realistic and have the
correct sign (orientation).
3. Track Data
•
Track Reference
– Is the track reference correct?
•
Track
– Is the track distance reasonable?
•
DMG
– Is the distance made good reasonable? How does it compare to the track distance? Is
it reasonably consistent with other measurements at the site? Good boat piloting is generally
indicated by how similar and consistent Track distance and DMG are.