Stationary Moving-Bed Analysis (SMBA)

Description

Teledyne RD Instruments introduced the StreamPro acoustic Doppler current profiler in 2003, which did not include an internal compass. During a stationary moving-bed test, the StreamPro and float often tend to swim or kite from the end of the tether (the instrument rotates then moves laterally in the direction of the rotation, see video of Streampro and resulting shiptrack). Because the StreamPro does not have an internal compass, it cannot compensate for instrument rotation. This rotation and lateral movement of the StreamPro on the end of the tether generates a false upstream velocity and an incorrect moving bed bias velocity. The vector dot product of the boat velocity and the unit vector of the depth-averaged water velocity has been shown (Mueller and others 2007) to be an effective method to account for the effect of the rotation and lateral movement. SMBA was written to apply the dot product computations to raw data files collected using the StreamPro software, WinRiver, or WinRiver II and to provide the user with the mean moving-bed velocity, the mean water velocity for the processed stationary measurement, and now in version 4.20 and later the ability to correct a discharge measurement for moving-bed bias based on one or more moving-bed tests.

The algorithms used in SMBA are documented in (Mueller 2007)

How to Download the Software

In order to provide support for SMBA and to provide an efficient means to communicate with users and allow users an efficient and organized means of providing suggestions and comments, SMBA can only be downloaded from the OSW Hydroacoustic Forums. To access the OSW Hydroacoustics Forums you must be a registered user of the forums.

Register for access to OSW Hydroacoustics Forums

Registered Users

Installation Instructions

1. Install the appropriate Matlab Component Runtime libary, if necessary. For instuctions on how to determine if you have the needed library and/or to install the library see Matlab Component Runtime Library Download and Installation
2. Download the SMBA executable from above.
3. Select a directory and unzip the SMBA to store the SMBA.exe adn SMBA.ctf files. These files must be in the same directory but can be in any directory.
4. Run the program by double-clicking on SMBA.exe in Windows Explorer or My Computer. You may wish to create a shortcut to SMBA.exe in a convenient location in the Start Menu or on the Desktop.

Operational Instructions

1. If you created a shortcut to SMBA.exe during the installation, you can run the program using the shortcut. Otherwise you can run the program by double-clicking on SMBA.exe in Windows Explorer or My Computer.
2. Select the units you wish to have the results displayed in. The units used to collect the data are independent of the units displayed in SMBA. This selection can only be made prior to processing the first moving-bed test.
3. Click the 'Load MB Test' button and select the stationary moving bed test raw data file (*r.000 or *.pd0) you wish to process. You may process multiple moving-bed tests but you must do them one test at a time. The name of the file you selected will be displayed in a box near the center of the window and a message indicating that the file is being read is displayed in red below the file name. When the processing is complete the graphs and results will be displayed. Be patient it takes some time for SMBA to read and decode the raw data file.

4. If a moving bed is detected a warning message will be displayed. You should read the warning and then click OK to close the message window. The main window will display the graphs and results from the computations. If a moving bed was detected the 'Adjust Q' button will become active to allow you to correct the discharge in the transects that comprise the measurement associated with the moving-bed test(s).
5. To adjust the discharge in the transects associated with the processed moving-bed tests, click the 'Adjust Q' button and select all of the transects that comprise the measurement. You may use click and drag, shift click, or control click to select multiple files. All of the files should be selected. NOTE: The transect files must be ASCII output files (*t.000 or *ASC.TXT).
6. A separate window will open to show the results of the discharge adjustment. If the window is not visible click the 'Show Results' button or if it says 'Hide Results' click it twice. The data shown in the Output Display window has also been place in the Windows clipboard so that it can be pasted into another application, such as, Word or Excel.
7. You may process another measurement without exiting SMBA by clicking the 'Clear All' button. This resets the program to accept a new measurement beginning with the moving-bed test(s).
8. Exit the program by Clicking the Close button.

Interpreting the Results

Distance Moved Upstream:

This is the distance the dot product algorithm has determined the instrument moved upstream relative to the measured water velocity. A negative number indicates the instrument moved downstream. This includes both real and preceived (moving bed) instrument motion.

Duration of Test:

This is the amount of time during which valid data were collected. Invalid bottom track data are not included in this duration.

Mean Moving-Bed Velocity:

The mean moving-bed velocity is computed as the numeric average of the moving-bed velocities computed for each ensemble. (Algorithms used in processing)

Mean Water Velocity:

The mean water velocity corrected for any detected moving-bed velocity. If the moving-bed velocity is negative, no correction is applied. The mean velocity for each ensemble is computed from the mean of the velocity vector components. The mean velocity of the entire measure is computed as the mean of the mean velocity magnitude for each ensemble, because the Streampro has not compass to measure velocity direction for each ensemble.. are averaged for each ensemble and the mean velocity. (Algorithms used in processing)

Mean Range from Xducer:

The mean depth for measurement is computed as the simple mean of thethe depth-weighted mean depth of each ensemble.

Potential Error (%):

The potential error is computed as the ratio of the mean moving-bed velocity and the mean water velocity expressed as a percentage. If the mean moving-bed velocity is negative this value defaults to 0.00. The user should consider a means to correct the measurement for bias caused by a moving bed when the potential error is greater than 1 percent. (See Oberg and others 2005)

Shiptrack Plot

The shiptrack plot is the resulting boat motion determined from the dot product of the boat velocity and water velocity unit vector. The reference is distance upstream along the y-axis and distance cross-stream along the x-axis relative to the water velocity. Note all the water velocity sticks are pointing straight down.

Cumulative Moving-Bed Velocity Time Series

This plot shows the cumulative mean moving bed velocity (y-axis) versus the duration of the data collected (x-axis). This plot can be used to ensure that sufficient data were collected for the mean moving-bed velocity to have reached an equilibrium value.