<p>The simple answer would be a potentiometer, as used for position feedback in a servo. You apply a voltage to the outer two contacts and measure the voltage at the moving, middle connection.</p>
<p>The next step would be a <a href="https://en.wikipedia.org/wiki/Rotary_encoder" rel="nofollow noreferrer">rotary encoder</a>. These should give you less friction and more accuracy, if you need it.</p>
<p>A camera would require significant processing power, but might be viable on a larger drone. Measuring α would be tricky with a camera on the drone, but you could calculate it from the distance from the centre and the length of the tether.</p>

CC BY-SA 4.0
2021-04-09T08:08:43.557Z
2021-04-09T08:08:43.557Z
Robin Bennett
<p>I'm trying to measure/estimate the position of a balloon, for that I need the two angles shown in the picture below. enter image description here</p>
<p><a href="https://i.sstatic.net/Cii8E.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Cii8E.png" alt="enter image description here" /></a></p>
<p>The idea is to place a helium filled balloon on a quadcopter to provide lift. As a first step, I imagined a fixed platform with the balloon attached. Next, I would like to estimate the value of the angles α and φ, since the length of the strap is fixed, getting the position of the globe is simply trigonometry.</p>
<p>The problem is that I am not sure how to measure such angles, what would be better and what type of sensor to use. I was thinking of some kind of optical sensor, but I'm not sure.</p>
<p>Can anyone suggest me some ideas?</p>

<hardware><recommendations><sensor><optical-sensor>
Estimate position of a balloon attached to a quadcopter
BobaFetty91
# Estimate position of a balloon attached to a quadcopter

(Asked by: username_0 on 2021-04-08)

I'm trying to measure/estimate the position of a balloon, for that I need the two angles shown in the picture below. enter image description here

[![enter image description here](https://i.sstatic.net/Cii8E.png)](https://i.sstatic.net/Cii8E.png)

The idea is to place a helium filled balloon on a quadcopter to provide lift. As a first step, I imagined a fixed platform with the balloon attached. Next, I would like to estimate the value of the angles α and φ, since the length of the strap is fixed, getting the position of the globe is simply trigonometry.

The problem is that I am not sure how to measure such angles, what would be better and what type of sensor to use. I was thinking of some kind of optical sensor, but I'm not sure.

Can anyone suggest me some ideas?

**Tags:** hardware, recommendations, sensor, optical-sensor

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## 1 answers

### Answer by username_1 on 2021-04-09. Score: 4

The simple answer would be a potentiometer, as used for position feedback in a servo. You apply a voltage to the outer two contacts and measure the voltage at the moving, middle connection.

The next step would be a [rotary encoder](https://en.wikipedia.org/wiki/Rotary_encoder). These should give you less friction and more accuracy, if you need it.

A camera would require significant processing power, but might be viable on a larger drone. Measuring α would be tricky with a camera on the drone, but you could calculate it from the distance from the centre and the length of the tether.


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