# Project to keep a buoy on water by gps at its exact location

I’m a beginner with arduino and electronics in general but I’m fascinated about the whole thing here.
To go into practice I made my own plant watering system on the simple base you can find here and by Ggl. (Nano, moisture sensor, relay, pump). New in this forum I hope to be in the right section for my questions.

Spinning around in my head: I would know if you guys see a chance to make the following prototype: The environment will be on a lake with mostly flat water but it can be windy. Think of a small man-over-board-buoy. Once its position is set the buoy keeps automatically this position and makes wind-drift corrections itself.

Classic, manual solution:

• Small cubic foam buoy, 10/10/10 cm or max. 15/15/15 cm which is swimming on water
• Cord and anchor at the ground to keep it at its predefined position

With Arduino logic and some small hardware

• Arduino nano, micro or something small and cheap
• GPS sensor for knowing the position and calculating the corrections
• Motors with function of a sort of jet or simple propeller drive
• Solar powered, needs running for at least 4 days

The logic should calculate the actual position by GPS. Compared to the predefined position by coordinates we know about the direction the buoy has to be moved. 2 Motors (each axis) able to run for-/backwards so that the buoy can be drived on the water to its location.

Questions

• What will be the best GPS accuracy today? It should keep the buoy in a radius of ~20 cm. Or is there any other technique to get in exact position?
• What about motors? Anything on market for moving water through a ~ ø 3 cm pipe like a miniature jet ski engine, through a pipe?
• What if I need at the end 1120 such buoys, each on a different position? You are right, it’s a 6 lanes rowing course (2000 m * 7 lanes * each 12.5 m a buoy).

Cheers.

The ducted 'fan' impeller is sometimes called a thruster - which could also refer to a single impeller mounted on a pivoting pod under the buoy. One propulsion motor (jet or impeller system), and one pivot motor could use less power overall - to be researched and tested.

20cm positioning will be tricky, but DGPS could work - if you have enough power/thrust. Your greatest single challenge will be power. Solar collector surface area, batteries, weight, motors, size of impellers to handle large corrections... etc. A spherical buoy will present a smaller wind-load surface == less power needed for correction.

A fun project, but it may turn out to be impractical due to cost and technology. These will be stolen as often as grandma's apple pie"

Cool project.

These guys seem to have figured something out that you might find useful.

Wave Glider Propulsion

Apologies I can't offer much help.

-Chase

I immediately see a problem here.

Although you can determine the actual position, and the desired position by using GPS, how do you know which way to travel, bearing in mind that a buoy is going to be continually rotated by wind/wave action?

Even with DGPS, your best obtainable position accuracy is about +/- 2 meters, and it can worsen to about +/- 100 meters depending on how many satellites are in view.

You will need sufficient battery power to last many days, in case of cloudy or stormy conditions. Your local climate is the guide.

I suspect a computer-control / GPS solution is not practical on a small scale because of power requirements and the instability of a small floating object.

I reckon you will need a compass as well as GPS so you can work out the direction to move to correct the position.

And you will also need an object that can move in a predictable direction. A sphere or a cube can’t do that - try a boat hull. Even then, the best hull shape only has directional stability when it is moving relative to the water.

…R

DGPS and newer technologies are good to well positioning under 1m.
The arbitrary rotation issue can be addressed several ways (compass etc), but nonetheless - I agree the feasibility of this getting beyond a really cool prototype is almost zero.

Wow, great estimates and tips. Thank you all. Never thought that more than a “forget it” will come back.
You mentioned right, the rotating body is a big challenge. And the accuracy of the GPS a second one. All in all it will maybe end in a heavy weight and big sized box. Battery, solar pannel, motors … feels no to fit in a 10 x 10 cm cube. I’m thinking about the buoy shape in all. It could be more in height because that’s not important. It has to be weighted/balanced so that the top is around 8 cm over water line. More height under water will make mor stability against wind drift.

We are now on work for the actual race next weekend. Here’s a short from two years ago, building up the race course with 1120 buoys on 7 lines by 2000 m. Total 14 km to do.

We keep on thinking and reporting back here.
Cheers, Christian

I do like the idea that an errant rowing shell can go crashing through the buoys and it won't get tangles and they will just motor back to position afterwards.

Battery life may not be an issue if they only have to be on the water for a few hours. Put the battery in the bottom for stability. Give them a radio signal to all come home to the dock for charging at the end of the day's racing and then in the morning drop them all in the water and they go back to their designated positions.

I'm imagining that two small thruster motors would be able to propel and direct the buoy. They would not need much more thrust than a bath toy.

cubecontrolninja: Never thought that more than a "forget it" will come back.

And indeed that is exactly all that should have come back. The vital bit is the last question. Not only is this an utterly stupid idea, but it's also utterly stupid idea multiplied by 1120.

I don't know how they lay out rowing courses but I do know that it is done with remarkable precision, and cross-winds and currents would have to be taken into account. I imagine there are stringent rules about laying out a course and maximum allowable buoy movement probably figures among them. The minimum you are asking for, but say nothing about, is that the buoys not only maintain their position absolutely but also maintain their position with the 1119 others i.e. if one moves, they all move in unison - and within the probable rules. You can be sure that you only need one or two of the 1120 buoys to not maintain their position properly and the managers of every team except the winning one will be screaming foul. And all that it might take to do that is one dud battery.

You can also be sure that if this idea was not absurd, somebody would have done it already, and you can safely bet they haven't. I guess this goes some way to explain the absence of rowing regattas on Lake Baikal.

Hi,

We are now on work for the actual race next weekend. Here's a short from two years ago, building up the race course with 1120 buoys on 7 lines by 2000 m. Total 14 km to do. http://youtu.be/mu_iG_zel60

Can you see my confusion. You all seem to be having fun, but for what end.

Who are Cube Control Ninjas?

Tom... :o

OKAY....I seee. To put the situation in two lines

Cube Ninjas setup boat race courses, involving buoys and lines. Cube Ninjas want to find out the feasibility of making an auto-positioning buoy so they don't have to do so much cable laying. Why didn't you say so?

Sounds cool.

I'd make the buoys look like a submarine that is submerged 30-40 cm, with a football shaped shaped float on the surface. The drive is provided by the submerged part, and the radio part is on top of the float. A small water jet is fitted in the 'sub'. It runs on a lithium battery. A Faraday generator in the stalk from the float to the sub keeps it charged, powered by it's bobbing motion due to the waves.

DGPS is a commercial technology, lisenced by the Department of Homeland Security. No doubt there is some overhead. Call the Coast Guard to find out what you need. Regular GPS - that you can do easily with an Arduino, and is free for the taking - gets you tenish meter precision. You might not need a compass. If you have 4 or more satellites, you will get an accurate direction of travel. The vessel will always be seeking the ideal position, yet will seldom attain it. Like sharks, your buoys will always be moving.

They should however, stay within a 10m radius circle (~314m^2). If this suits your needs, then yes it is doable with a home-made Arduino based device. Otherwise, you will need more horsepower.

TomGeorge: Cube Ninjas want to find out the feasibility of making an auto-positioning buoy so they don't have to do so much cable laying. Why didn't you say so?

Indeed.

Then we would have immediately answered as @Nick_Pyner has done in Reply #9

...R

Nick_Pyner: The minimum you are asking for, but say nothing about, is that the buoys not only maintain their position absolutely but also maintain their position with the 1119 others i.e. if one moves, they all move in unison - and within the probable rules. You can be sure that you only need one or two of the 1120 buoys not maintain their position properly and the managers of every team except the winning one will be screaming foul. And all that it might take to do that is one dud battery.

Unison movement will be only if the buoys are connected or referenced to each other. That's not the idea. If each one is taking its position by its own GPS we will have 1120 independent buoys. If one is out of order, drifting away, the others are still on place.

cubecontrolninja: If one is out of order, drifting away, the others are still on place.

If one out of 1120 is out of order, drifting away, you can be sure that several others will be - or are just about to be. But if that's OK by you, go for it. We look forward to the entertainment on Lagoa Rodrigo de Freitas later this year.

Why not hard tether/anchor every fourth or fifth buoy and have the free floating buoys reference their location with respect to the closest stationary buoy? Could potentially do away with GPS that way. I'm sure if you're clever enough there's some sort of laser or imaging capabilities out there that could be used as the signal for needed corrections.

Keep in mind, i've never done anything like this... so hold the feasibility of the above lightly haha.

-Chase

I will say, there's a fine line between having enough experience to confidently say "something like this will NEVER work!" and believing something can't be done simply because it's never been done before.

I suppose time will tell with this project, but I find it hard to stomach when people are so quick to kill an idea at it's very onset. What's the harm in brainstorming a bit you know?

cbrum11:
Why not hard tether/anchor every fourth or fifth buoy and have the free floating buoys reference their location with respect to the closest stationary buoy?

That assumes that the problem is with knowing the position whereas IMHO the problem is with keeping the position.

What’s the harm in brainstorming a bit you know?

Brainstorming is great - but planning a system with 1120 buoys when you have not even get one to hold position is not what I call brainstorming.

…R

Brainstorming is great - but planning a system with 1120 buoys when you have not even get one to hold position is not what I call brainstorming.

Fair enough. 1120 is a hell of a lot of buoys.

Sure is a nice fantasy, though!

Just imagine 1120 buoys racing away from the dock, all to line up neatly and form a racetrack.

cbrum11: Why not hard tether/anchor every fourth or fifth buoy and have the free floating buoys reference their location with respect to the closest stationary buoy? ............... What's the harm in brainstorming a bit you know?

I understand one of the objectives was to avoid laying 14 000m of line. I think you might have achieved that. Instead of laying 14 000m, i believe there is quite a possibility that they will now only need to lay out 13 300m of line. I guess that's brainstorming for you.