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Nick, you’re welcome!
In NVE, we almost never use GPS for regular ADCP measurements,so we have no systematic storage for baty data. Sorry for that.Kristoffer
Manufacturers are welcome, and like Dave says (and all probably agree on) no promoting or advertising.
Except posts this: “TRDI would like to announce that we have released the StreamPro2. It is the size of a pencil and measures from 0-10 meters”. (Announcing new instruments and new software, as long as they manage to stay on the right side of “no advertising”)
I think that for now, we should not have any more subsections.
If use of the forums really takes off, we could add subsections later on.
Hi
In NVE (Norway) we only have regattas where test them against each other on an irregular basis. (Aiming at REGULAR basis, but we don’t manage to do so)
Kristoffer
Hi Alex and all.
I have seen something similar on a StreamPro measurement as well. Overestimation of speed in the 5th bin. Depth around 1-1.3 meters, down to 2 meters. ARC boat. Clear water in the outlet of a lake. I don’t know what this is. If it was some double reflection phenomena the erroneous velocity should have followed the shape of the river bed.
I have used this instrument many times and this is the only time I have seen this happen.
Any ideas?
Kristofffer
PS: I know it was too shallow for the ARC boat to be ideal here. DS
Mini-SUP? I hope the propellers do not push water past the adcp. In the drawings on the homepage it looks like they do!
Hi, Alex.
I have not seen this in a discharge measurement, but I have seen a similar feature in a test with a RiverPro anchored in a lake. I really hope I would have noticed it in my own discharge measurements, and I have had a new look at some of them now without seeing the feature. The anchored riverpro shows a HIGHER velocity magnitude (and east and north velocity) in the first bin below the surface bins in WinRiver when I average a lot of ensembles. See attached screenshot. (The reason it was anchored is that we used the data to check if a still lake was actually still when testing fro flow disturbance). If not averaging, we only see low velocity magnitudes in the top bins and higher velocity magnitudes in the rest of the bins, since they are more noisy.
To state the obvious: It must be something wrong in the Emlid VTG data. Either the output or the readings. Or in the RS5 VTG reading.
Is it possible to connect another gps (another brand) to the rs5 to see if you have the same issue? If so, the issue is how the RS5 reads/interprets the VTG data. Another suggestion: If it is possible to connect the Emlid to a PC/PDA/phone and read VTG data, try walking north at 1 m/s and check if VTG data agrees. (Or: Return GPS and rs5 to manufacturer/dealer and tell them that something is wrong)
I did not read your post well, it seems. Nor did I recognize the colors. Shame on me! I have no idea why VTG runs away from GGA and BT-track. Have you ever seen OK data from this GPS unit?
An offset that is supposed to be 5.0 degrees that has been entered as 50 degrees by accident?
Kristoffer
One more possible problem: Will these discharge measurements be used to make a rating curve for a gauging station? If so, you need to collect stage just as often as discharge, and you need to check if there is a time delay between the location where you measure discharge and the site of the stage measurements.
Hi. I am not familiar with the expression “regulated flow conditions”. Does it mean that discharge is changing rapidly due to opening/closing of upstream hatches/locks/turbines in an upstream dam? If so, I really don’t know. Perhaps, if you have 4-6 (or more) transects and you see a linear trend, you could calculate Deviation from trendline (and not from mean) and use the MPRR condition on that deviation?
For a steady flow NVE (Norway) have 3 conditions
– Even number of transects
– 12 minutes at least of total time (this comes from USGS + Qrev/QrevInt)
– No “red transects” in WinRiver, that is, no transect more different from the mean than the MPRR condition in WinRiver (https://www.researchgate.net/publication/305650623_Estimation_of_Type_A_uncertainty_of_moving-boat_ADCP_streamflow_measurements)
The last condition is encouraged also when using RSL (with Sontek ADCPs), even if the operator need to bring a table to check MPRR versus number of transects. For a very bad site, we may allow “red transects” after collecting 8-12 transects, if it seems obvious that we will not manage to avoid the “red transects” within a sensible amount of time.
In addition, if we QrevInt to process data on site, and we use the Oursin uncertainty model in QrevInt. If we see that COV (covariation, difference between transects) is not the biggest source of unsertainty, then we know that we have enough transects, and that to reduce uncertainty we need to improve somtehing else.
Great. Thanks. NVE will probably buy a vector gps quite soon, but I need to find out what the advantages and disadvantages are. I hope that using vector gps means I will not need to spend half an eternity trying to calibrate the adcp compass any more.
