Forum Replies Created
-
Replies
-
Nick sent this email to me:
1 and 4 are closely related.
…..I have this vision that we gradually build up a database of river bathymetry (or at least cross-sections) from our ADCP data, and then start to add to it the hydraulics, so we can have the essential foundations in place to enable non-contact observations all over the place…! Velocity mapping tools may be a part of this….
I also was unaware of this company. I put together these tables to give me some idea of how it compares to other ADCPs. The info comes from manufacturer’s specifications. If I have anything wrong, please fee free to provide a correction here. I only showed the information for the 1200 kHz. They don’t say this explicitly but I think that the 600 kHz has a larger diameter, perhaps because the transducers are larger?
Libor:
I know several groups in several different countries in South America who would love to have some instruments that work, even older ones. They are desparate for instrumentation because it costs many times more for them to get an ADCP due to duties, unstable currencies, etc. In some cases the cost of an ADCP would be 3 times the salary for a well-trained professional.
I could make some inquiries with them about it and see if they or someone they know could assist you. For one example, the current secretary general of WMO is the former Director of the Argentinean National Meteorological Service and is known to several people who work with me in hydroacoustics.
Daniel
I will do what I can to assist. I am not so good with making changes (meaning editing) to the web pages but can suggest ideas for what could/should be there and how it might be present.
Kevin
So, is it your sense that the failure rate is acceptable? I used to hear from Data Chiefs and others that Flowtrackers failed too often. Of course, old school streamgagers would say something like ‘our current (mechanical) meters didn’t break so often’.
Kevin
It would be good if USGS would comment on this. When I was still there, the failure rate of FTs was a concern.
FWIW – I agree with Dave and others. It is more or less what we did when at USGS for the USGS HA forum.
Thanks Travis….
Assuming that is something that we want to do, could you help with it? I expect that Daniel would be glad to have the help.
Kevin
I don’t have strong opinions on this, but I don’t think it is up to me. Conversations on Monday were helpful.
I think that Jeff describes it well. A bit more detail is provided in https://hydroacoustics.usgs.gov/memos/OSW2009-02.pdf. I have pasted in the pertinent wording below.
For each ensemble, WinRiver calculates a depth below which velocities measured by the ADCP are not used due to possible errors caused by side-lobe interference. This depth is referred to as the side-lobe cutoff. In previous versions of WinRiver (2.02 or earlier) the sidelobe cutoff was calculated as 6% of the depth, computed as the mean of all valid beam depths for an ensemble (figure 1a). The new side-lobe cutoff is calculated as 6% of the shallowest beam depth in an ensemble (figure 1b). For example, the side lobe cutoff computed for ensemble 78 in figure 1 for prior versions of WinRiver II is 2.4 ft. The beam depths measured for this ensemble were 1.9, 3.5, 3.3, and 1.7 ft. The new side lobe cutoff, computed using WinRiver II version 2.03 and 2.04 is 1.6 ft. The change in the side-lobe cutoff may result in fewer valid depth cells in ensembles near sloping banks and in cross sections with irregular or rough streambeds. As a consequence, the middle (measured portion of the cross-section) discharge will decrease and the bottom (unmeasured or extrapolated portion of the cross-section) discharge will increase.
OSW has used the new version of WinRiver II to reprocess discharge measurements from Oberg and Mueller (2007) as well as other available measurements. Based on the discharge measurements reviewed to date, the new side-lobe cutoff has resulted in a median difference in discharge of +0.5 percent. The typical change in discharge was less than 1 percent. However, for about 4 percent of the discharge measurements reviewed the discharge changed by more than 5 percent. The largest changes were found for measurements made in shallow uneven cross sections that would typically be considered poor measurement sections. These cross sections are characterized by mean differences of beam depths for individual ensembles ranging from 17 to 32 percent.
Measurements collected in the 2009 Water Year with a mean difference of beam depths in individual ensembles exceeding 15% or a mean number of valid depth cells per ensemble less than 4 must be reprocessed using version 2.04.
Ole
In the US (and more specifically, the USGS), QRev discharge computation algorithms are the ‘standard’ for all moving boat ADCP discharge computations. It is a requirement in the USGS. This is one of the reasons that QRev was written. Many (most?) other agencies in the US track what the USGS does and therefore, I suspect that most would be using QRev, but I have no proof of that. I am sure that Dave Mueller can provide even more information than this.
Kevin
