Collecting Under Ice 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 under ice 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: 1280 x 720

Date Taken:

Length: 00:04:10

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 under ice 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, and ensure the depth and velocity readings shown on the plots are reasonable. It’s also important to review intensities and velocities to determine if there are spikes caused by slush near the transducer face. 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. This will open up a dialog with the information for your next vertical. For an ice measurement, make sure you select the ice extrapolation method, which uses a no slip on the top and bottom. A separate video describes the process of evaluating extrapolation during measurement review. You’ll notice the options on the right change based on this entry. Make sure that if the water surface has dropped below the ice, the ice method should not be used, as the surface velocity is not going to zero. 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 ice information shown here is useful in that it will make the graphs in SxS Pro represent what the river actually looks like. However, this ice information is not required for computation of discharge in the software. This diagram shows the various fields related to the ice conditions and how they should be measured. These measurements are usually based on the water surface, as you can see. If you enter the ice information, the ADCP depth below ice will be computed based on your entries. If you chose to leave out the ice information, you will simply enter the ADCP depth below the ice. Be aware that this value will carry forward from one vertical to the next, so if the value varies, you will need to be sure it’s being updated.

With under ice measurements, we should be using the y-velocity method, which requires the ADCP to be held at a fixed orientation to the tagline, with beam 3 downstream. When this is done, no flow angle information is required here. If you are using magnitude velocity method, because let’s say you have no way of orienting the ADCP, you will not enter flow angle information as you can’t measure the flow angle on the water surface. Measuring angles for under ice measurements is covered in another video.

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 reject the vertical and select 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.