I recently used a Blue Robotics aquatic drone for the first time to measure the bathymetry of a small agricultural pond. The drone had a velocity of 2.5 m/s and was set to 5 m intervals with 1 m turnaround spacing. About half of the depth points exceed 7 m (a number are around 60 m+ in depth). The pond obviously isn’t that deep. The other half of the data points are more reasonable, around 2–3 m depth.
Is it normal to have a significant (~50%) number of depth points that are excessively large? Does anyone know what might have caused this?
That sounds like an interesting survey - do you mean you used a BlueBoat? 2.5 m/s is quite fast for survey speed! Were you using a Ping single beam sonar?
For the points that measure 60m+, what is the confidence value? I would guess very low - as those sound like erroneous readings. Slowing down your survey speed is likely the easiest change to get better data! At high speed, bubbles around the sonar can cause low-confidence readings - filtering based on confidence, as described in this guide, can eliminate outliers…
Thank you! Yes, I mean the BlueBoat. I believe it was a Ping single beam sonar. I’ll take a look at the guide for confidence readings. Could there be issues too from sampling a pond with a soft, muddy base, dirty water, and shallow depths?