Hi, my name is Nick Stasulis and I am a hydrologic technician with the Maine office of the New
England Water Science Center.
In this screencast I will discuss how you can perform a more advanced review of data
collected in SxS Pro, when needed.
First, let’s start with one important point.
This advanced review is not something that should be done or needed for most midsection
data collected in SxS Pro.
Proper review during the measurement and at the site once the measurement is complete
should eliminate most issues that would need this detailed advanced review.
Collecting good quality data will allow you to eliminate most of these issues, if they
are detected and addressed during data collection.
That said, let’s take a look at a measurement that has some irregularities.
Notice the very slow velocities at the surface nearly in every vertical.
The velocity profile plot indicates this data is large magnitude negative velocity, which
is likely not realistic.
We see in the contour plot that water error velocities are fairly high in some of these
bins, but not all.
We have the ability to change the error threshold for each vertical, or the up threshold for
the entire measurement, but there are no good tabular views in SxS Pro to determine reasonable
values.
Rather than use trial and error, let’s load this data into WinRiver II so we can utilize
the better data viewing options there.
First, open BBSlice, a program that comes as a part of RDI Tools.
For the input file, select the pD0 for the measurement, which is the raw data file.
For the output file, I like to use Sliced, which will create a file for each vertical
named Sliced000, 001 and so on.
Click the Slice button and the utility will create a new output file for each vertical,
and will include unused verticals.
In the measurement directory, we now see the new sliced data files with the .000 extension.
In WinRiver II, select create measurement from data files, navigate to the measurement
directory, type *.000 in the file name box, and select all of the sliced files.
For each vertical, now a transect, you will get a warning box stating there is no associated
configuration file.
Simply click ok for each.
You’ll notice in the playback configuration that there are no processing settings, no
transducer depth, or other information, it is simply the raw ADCP data.
You could enter this information, but we will leave it as is for the purpose of this data
review.
You will also notice the reference is set to bottom track, which could cause errors
if there was a significant bias in the bottom track data, so consider changing the reference
to none.
Now that the raw data is loaded, you can reprocess each transect, essentially allowing you to
review one vertical at a time, with access to the tabular and graphical options in WinRiver
II that are not available in SxS Pro.
In this measurement, we were seeing negative velocities near the surface that seemed to
be erroneous in SxS Pro.
Brining up a velocity tabular allows us to see that most of the error velocities near
the surface are high.
Our water track error threshold in SxS Pro was set to 1.969, which is high enough that
it really isn’t screening much of the invalid data near the surface.
Scanning through the velocity tabular in WinRiver II for several verticals indicates a value
of about 0.5 would remove most of the data near the top with high velocity error values.
Back in SxS Pro, we note an as-is discharge of about 18.3 cfs for this measurement.
We can first go into the Processing dialog and set the good ensemble to cell setting
to 5, which will force the software to require 5 valid ensembles to compute a bin at each
depth in the vertical.
Then, we go into each station and manually change the error threshold to 0.5.
Be sure to check the profile plot and ensure all of the invalid data is being screened.
If you still see erroneous values, decrease the threshold value, and if you feel too much
data is being screened, increase it so the erroneous values are removed, but enough valid
data remains.
Once all the erroneous data is removed, the final discharge is around 46 cfs and looks
much more reasonable in the contour plot and profile plot, though the indicated angles
are inconsistent.
You would want to be sure to document in your notes what changes were made and how the values
you applied were determined.