Collecting Open Water Midsection ADCP Measurements in TRDI SxS Pro

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Detailed Description

In this video, we will demonstrate how to collect data at a station as part of an open water midsection ADCP measurement in TRDI SxS Pro. Note: Use of trade names is for descriptive purposes only, and does not imply endorsement by the USGS. For additional videos in this series, visit the following link: https://www2.usgs.gov/humancapital/ecd/hydrotube/hydrotube-ADCP.html
 

Details

Image Dimensions: 480 x 360

Date Taken:

Length: 00:03:50

Location Taken: Augusta, ME, US

Transcript

Hi, my name is Nick Stasulis and I work with the Maine Office of the New England Water Science Center. In this video, we will demonstrate how to collect data at a station as part of an open water midsection ADCP measurement in TRDI SxS Pro.

Here we see the starting edge information has already been entered and the unit is pinging, ready to begin collecting data. Of course, before starting data collection, ensure the ADCP is getting a reasonable number of bins, here, and ensure the depth and velocity readings shown on the plots are reasonable. If needed, be aware that you can stop pinging and go back into the wizard by selecting Configure > Measurement Wizard to change the ADCP configuration based on the data you are seeing.

Once you are getting reasonable data, select F5, or click the Next button here. This will open up a dialog with the information for your next vertical. For an open water measurement, it is generally recommended to leave the extrapolation method set to Power/Power, which is the default, and evaluate the extrapolation once the measurement is complete. A separate video describes the process of evaluating extrapolation during measurement review. The water track error velocity is populated by the software based on the unit and configuration, and is typically not changed.

Any comments about the vertical can be entered in the notes here. An alternative is to make your notes in SVMobile, which would allow you to make notes about a specific vertical before, during or after data collection at that vertical.

Next, enter the location of the vertical, as a distance from the initial point. Let’s say we are at 15 ft. The ADCP depth should be measured, and in this case, let’s say we are using a StreamPro on a trimaran, with a transducer depth of 0.17 ft.

Next, since we are using the magnitude velocity method in this open water measurement, we need to account for the angle of the flow through our cross section. To do this we assume the alignment of the boat is approximately equal to the mean flow direction.  I prefer to use either a contractor’s angle measurement tool, a paper note sheet or a protractor. After you measure this angle or coefficient, notice that you can enter an angle, like 8 degrees, or a coefficient, like 0.99. Either way, ensure you are measuring and noting these angles for every station, as there is no automated angle correction for open water measurements. You may find it useful to determine the azimuth of the cross section to use as a tool for confirming your noted angles. A different video describes the process of accounting for angles in open water in more detail.

Lastly, select your water depth source. For all ADCPs, bottom track is an option, which is the 4 beam average depth. Selecting bottom track here does not mean the ADCP will be bottom tracking to determine movement. If your ADCP has a vertical beam, that can be selected and you’ll notice composite is an option too. Composite will give preference to the vertical beam, if it’s valid, and use bottom track otherwise. Also manual depth is an option, which allows you to enter a manual depth reading in place of an ADCP depth reading. We’ll discuss the use of manual depth in another video that deals with invalid depths. Typically, you can leave the depth reference set to bottom track. If you observe issues when trying to collect data, you can abort the data collection for the vertical and try selecting vertical beam, or manual depth, as needed. If a manual depth is used, be sure to document how the manual depth was obtained in the notes.

Once you are satisfied with the information you’ve entered on this dialog, click Record to begin the 40 second data collection.