YSI SonTek RiverSurveyor, System Manual

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SonTek/YSI Inc
RiverSurveyor System Manual (May 1, 2007)
84
6.6.7. Profiling Range – Number of Cells, Cell Size, and Blanking Distance
The
Profiling Range
settings in the
User Setup
dialog box (
Figure 6-6
) determine the depth range
over which velocity data will be collected. It is critical that the profiling range you set is greater
than the expected maximum depth for your transect. This is because profiling to a depth shal-
lower than the actual water depth will leave the remaining depth unmeasured. It is better to use a
larger estimate of the maximum expected depth to reduce the chance of losing velocity data.
If you do not know the maximum depth for the section, set the profiling range equal to the
maximum profiling range of the system (
Table 3-1
), and then make a single measurement across
the transect. After this transect, go to the
Discharge Calculation
dialog box (
Figure 5-5
;
Process-
ing|Discharge Computation
or
Ctrl+D
) to view the
Maximum Depth
that was recorded. Based on
this maximum depth, you can then repeat the measurement with new profiling parameters.
The maximum profiling range is calculated as:
Profiling Range = Blanking Di (N + 1/2) x Cell Size
where
N
is the number of cells.
After you have determined the maximum expected depth, you can let the RiverSurveyor program
calculate the profiling parameters automatically (
Method 1: Select maximum depth
), or you can
enter the profiling parameters manually (
Method 2: Input values manually
).
Using
Method 1
will automatically set all the profiling range parameters using only the maximum
depth across the entire section or area.
To use
Method 1
(
Figure 6-5
):
1. Enter the
Maximum Depth
you expect for this section (or series of transects if you are collect-
ing multiple series of transects at one time). Remember, it is better to use a larger than ex-
pected value (
see above description ). The values displayed in the
Method 2
fields will update
as you enter the maximum depth.
2. If the computed values for
Number of Cells
,
Cell Size
,
Blanking Distance
, and the
Profil-
ing Range
do not seem appropriate for your
application, either enter a different depth or
adjust each of the values accordingly. Note
that the
Profiling Range
will always display a
range greater than the maximum depth that
you entered for
Maximum Depth
.
To use
Method 2
(
Figure 6-5
):
1. Refer to
Table 3-1
(
Summary of RiverSur-
veyor Specifications and Configurations
) to
find the minimum blanking distance for the
frequency of your ADP. Enter this value into
the
Blanking Distance
field. Example: A
3-MHz ADP has a minimum blanking dis-
tance of 0.2 m (0.66 ft).
2. Consider the resolution of velocity data that
you will need for this application. Refer to
Table 3-1
for the minimum and maximum
Figure 6-5. User Setup – Profiling Range