Loop Correction Software (LC)

Description

Loop Correction is a computer program written to determine if a moving bed is present from the loop method data and to correct the measured discharge using the distributed correction method. The computer program reads ASCII files in the standard ASCII output format from Teledyne RD Instruments WinRiver. SonTek/YSI RiverSurveyor can also output files consistent with this format. The LC program first requests the user load the loop data file. The mean moving-bed velocity is computed and the direction checked to verify that it is in the upstream direction. The criteria for determining if the data reflect a moving bed are applied and reported to the user. If a moving-bed is detected, the user can select the files (transects) for the discharge measurement. The program will read the files and compute the corrected discharge. The results of the entire process are displayed for the user and can be saved to a file and printed for inclusion in the measurement archive. Details of the loop method including proper field techniques are documented in:

OSW Technical Memorandum 2006.4

Scientific Investigations Report 2006-5079

How to Download the Software

In order to provide support for LC and to provide an efficient means to communicate with users and allow users an efficient and organized means of providing suggestions and comments, LC 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 LC executable from the OSW Hydroacoustic Forums described above.
3. Select a directory and unzip the LC to store the LC.exe and LC.ctf files. These files must be in the same directory but can be in any directory.
4. Run the program by double-clicking on LC.exe in Windows Explorer or My Computer. You may wish to create a shortcut to LC.exe in a convenient location in the Start Menu or on the Desktop.

Operational Instructions

1. Review the loop file in the manufactures data collection and processing software. Check for excessive bad bottom-track data and other problems that could reduce the accuracy of the loop. Record any observed problems.
2. Review and process the discharge measurement files. Use appropriate U.S. Geological Survey guidance and policies to determine the mean unadjusted discharge.
3. Generate Teledyne RD Instrument Classic ASCII output compatible files for the loop and discharge measurement files.
4. If you created a shortcut to LC.exe during the installation, you can run the program using the shortcut. Otherwise you can run the program by double-clicking on LC.exe in Windows Explorer or My Computer.
5. Click on the "Select Loop File" button, and browse for the ASCII output of the loop measurement. The program will process the loop and determine if a correction is required. The "Select Measurement Files" button will become active. If no correction is required, proceed to step 7.
6. 6.If a correction is required, process the discharge measurement files with LC. Click on the "Select Measurement Files" button. Select the ASCII output for all discharge measurement files using Control and Shift click to select multiple files (standard Windows multiple file collection procedures). The program will distribute the moving-bed correction to all ensembles and provide both an unadjusted and adjusted final discharge.
7. 7.Save, print, and file the results. Click on the "Save Results" button to save the results to a text file. Print the text file and attach the printout to the hardcopy field notes. Place the text file in the corresponding directory with the rest of the measurement files for archival.
8. Exit the program by Clicking the Close button.

Interpreting the Results

When using the loop method, a measured mean moving-bed velocity of at least 0.04 ft/s indicates the presence of a moving-bed. If the measured moving bed velocity exceeds 0.04 ft/s, the ratio of the mean moving-bed velocity and mean water velocity is computed by dividing the mean moving-bed velocity by the mean water velocity. If this ratio is greater than 0.01, the apparent bed movement will cause at least a 1-percent negative bias in the computed discharge and correction of the discharge is recommended.

If the loop closure error is not in the upstream direction the program will determine that there is NOT a moving bed. If there appears to be a moving bed but LC does not recommend corrections check, the moving-bed direction be compared to the flow direction. The moving-bed direction should be approximately 180 degrees (+/- 45 degrees) from the flow direction.