mesurements under water

Does anyone have experience using a drone to measure the depth of a pond? I understand using DroneDeploy I can get terrain models and estimate the depth of an open pit. But if the pit was full of water, would the drone “see” the bottom? Do I need a FLIR camera?

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Yes, you would need Lidar or a measurement to project the surface in CAD from the water level to the bottom.

MichaelL, I joined/posted a few days ago asking a similar question.
Instead of Lidar or depth soundings, would the blue wave of a multispectral camera penetrate the water surface?

I really don’t know anything other than what I have read on this type of capture/surveying, but I would imagine that it would be affected by the depth of the water before you need sonar and the condition of the water is there is vegetation?

Even LiDAR has limitations penetrating water. Unless the water is extremely clear, it can’t measure more than a couple of meters at best. RGB is even more limited, basically WYSIWYG. And like Michael stated, it will be affected by weeds/algae, sun angle, besides turbidity, waves, etc.

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Thanks GeoTech! Those limitations would actually serve as interest points for the conditions I’m hoping to remedy— identifying SAVs (sub aquatic vegetation), monitoring turbidity/plumes, and surveying in depths not readily accessible by sonar (i.e. less than 1-2 meters).
It sounds like I just need to convince someone to buy me a P4 Multispectral to test it out! :thinking:

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We have done a few lake bottom and river bottom mapping projects. For small projects we have found that this USVs | Seafloor Systems Inc works pretty well to get the information that we need. We are an engineering/survey company so we already have the full gamut of GPS equipment needed to make it fit our needs. We have seen that if we are lucky we might be able to pull some data from the aerial images if the water is still enough and clear enough but we don’t ever use it for true design work.

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I also just learned that there’s also something called Bathymetric Lidar: Bathymetric Lidar | Hydro International. I have no idea how it works, or if it could or will ever be available to drone users.

This piece from their first artical is great! All of these issues are overcome by control and point cloud editing software, but I noticed that everything stated “coastal” so I don’t think it applies to situations where the water gets deeper than a certain point, is murky or has vegitation.

“We investigated the most significant issues affecting the creation of a littoral zone digital elevation model from overlapping bathymetric and topographic Lidar (light detection and ranging) data. The main challenge was found to be the use of different methodologies used to establish vertical datums, as well as the narrow overlap between the two data sets, lack of ground control points and data gaps. We identified the main causes of gaps in bathymetric Lidar data and outline a new procedure for quantifying their occurrence.”