I know very little about drones, but I'm trying to learn if collecting river samples is something that could be done autonomously using commercial drones?

  • Is it possible to give the drone some coordinates of the river and have it go and collect without further input?
  • Is it even legal to do such a thing without someone controlling?
  • If it's not possible to do autonomously, how much input would be needed from a controller?
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    $\begingroup$ Legality would depend on where you are. Which country are you working in? $\endgroup$ – BillThePlatypus Jun 20 '20 at 18:40
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    $\begingroup$ Since you want to get samples from a river, can an automatic ship be an option? Its legality might be easier to solve. People got crazy about anything flying, but not on wheels/in water. Might be even easier to build. $\endgroup$ – Nyos Jun 20 '20 at 21:21
  • $\begingroup$ Check out the snotbot. They do something similar, only on the open ocean. $\endgroup$ – Kenn Sebesta Jul 22 '20 at 1:24

Autonomous operation isn't a technical problem. For example, DJI's drones are capable of flying themselves back to the launch point if the signal from the remote control fails.

The problem is legality.

Most drones are required to be flown within the operator's line of sight. The reason for this isn't because the operator has to be actively controlling the drone -- a fully-autonomous drone is perfectly legal -- but because the operator is responsible for collision avoidance.

If you've got an operator watching things, ready to take over if a problem arises, a self-piloting drone is perfectly legal. If, on the other hand, you want something that's completely unattended, you'll need to work with your local regulatory agency to get permission, and that's going to be a difficult thing to do.

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    $\begingroup$ There are people (both academic and industry) working on different schemes for automatic air traffic control for drones. It's a field with active research going on, so this might change soon. $\endgroup$ – nick012000 Jun 20 '20 at 6:26

Absolutely this is possible - in the UK, Imperial College London have built an aircraft to do exactly this, which they say

"dives like a gannet and launches like a flying fish."

The launch is needed to break surface tension with a small drone, which otherwise makes the take-off difficult.

You could also use a multirotor or helicopter design, and hang a Nansen/Niskin bottle under the aircraft, dip it to the needed depth and close it (e.g. release a messenger weight.) If you know the length of the string and drone altitude you would know the sampling depth. Depending on what you are sampling for, you may need to include sensors to make some in-situ measurements (e.g. temperature.)

This could be executed automatically with most current autopilots - just set the Latitude, Longitude and Altitude needed for the dip. Regulations will vary by jurisdiction and, again, depending on your exact requirements. In the UK for example, doing this under visual line of sight (VLOS) rules should require no further paperwork but for Extended or Beyond VLOS, this would require an Operating Safety Case approved by the CAA. Essentially you just have to think about what could go wrong, and explain how you will keep the risk as low as possible - possible safety mitigations may include:

  • Stay over the water - lowers the chance of people under the aircraft and ground hazards
  • Stay as low as possible - reduces the risk to aircraft (be aware that rivers are often used by helicopters for navigation, and in many cities some helicopters (e.g. single engine) need to fly over rivers for safety reasons.)
  • Publish NOTAM and liaise with local ATC
  • Use of an aircraft with redundant flight-critical components
  • If the collection site is in EVLOS, manual override available to shore-side observer
  • If BVLOS you will need some form of monitoring and recall/abort.
  • Approved Electronic Conspicuity device (required for BVLOS in the UK) for visibility to others
  • Detect-and-avoid capability

These are non-exhaustive examples - but the CAA are usually quite helpful with their feedback when making such applications.

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    $\begingroup$ That's very cool. But I think that what Imperial have built there is much more sophisticated than what we would need. Their aircraft is diving right down in the water. For our purposes, I was just imaging that there would be a little bottle on the bottom of the drone, and the drone could just lower itself and get a little water in the bottle. There are two separate things here. (i) Navigating to the river autonomously given some coordinates and (ii) collecting the water sample. I can see that (ii) might require some clever solutions but is (i) the kind of thing that can be done routinely? $\endgroup$ – user1551817 Jun 19 '20 at 17:30
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    $\begingroup$ I'm fairly sure you could hang some form of Nansen/Niskin bottle under a multirotor, dip it to the needed depth and close it (e.g. release a messenger weight.) If you know the length of the string and drone altitude you would know the sampling depth. You could probably collect a larger sample this way whereas Imperial's fixed-wing design may allow for longer flights to the sample point; it all depends on your specific needs. You should be able to program this behaviour into an autopilot like any waypoint - set Lat, Lon & Altitude for the dip. $\endgroup$ – Kralc Jun 19 '20 at 20:24

I'm not sure about legality, but I think Arducopter could be used for the task required.

It has full GPS waypoint mission capability and many mission tasks. I believe one that would be applicable is the package place command: https://ardupilot.org/copter/docs/mission-command-list.html#package-place

This allows it to descend to drop package. It could be combined with a servo command: https://ardupilot.org/copter/docs/mission-command-list.html#do-set-servo

These are all documented in the arducopter docs: https://ardupilot.org/copter/index.html

Based on your previous comments it seems like it would work for the task at hand.


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