# Can You Validate Earth's Curvature with a Drone?

#### Kriss3d

##### New Member
First of all. I know earth is a sphere. I got the idea that since we with a theodolite can see earth curve directly, I think a simple experiment could be used to more specifically prove the famous drop.

A theodolite set up exactly level,
A drone flies out over the ocean keeping in the center of the crosshair at all times. Or at least when taking readings.

A method for a drone to measure the exact distance from itself down to the water below. My initial idea would be a laser range finder. But I'm not sure if that would work on water
Or would an ultra sonic work better?

Is there any known way to accurately determine distance to something bouncing it off water Or will a simple altimeter using air pressure be accurate enough ?

#### cloudspotter

##### Senior Member.
The first problem that springs to my mind is the range of a drone. From a quick Google is seems that 5 miles is about the limit and that's with a drone that costs over a thousand pounds

#### DavidB66

##### Active Member
The first problem that springs to my mind is the range of a drone. From a quick Google is seems that 5 miles is about the limit and that's with a drone that costs over a thousand pounds
On the question of range, I don't think it would be strictly necessary for the drone to fly all the way from the observation point to the target distance or distances. It could be carried out on a boat and then launched to rise until it reaches the crosshairs. (Radio communication between the boat and the observer would presumably be necessary.) I don't know if this would meet the purpose of the experiment, because I'm not sure what the purpose is! There are already several videos by Jesse Kozlowski showing the size of the 'drop' through a theodolite aimed at some distant lighthouse, etc. This has no impact on flat earth believers, because (a) they don't understand the geometry, and (b) they don't trust theodolites.

#### cloudspotter

##### Senior Member.
On the question of range, I don't think it would be strictly necessary for the drone to fly all the way from the observation point to the target distance or distances. It could be carried out on a boat and then launched to rise until it reaches the crosshairs. (Radio communication between the boat and the observer would presumably be necessary.)

Good point, that would get over the range issue

On to the point of measuring height; I'm thinking a simple plum line hanging from the drone with a highly visible weight on the end would at least indicate if the water surface was dropping away from the crosshair height

#### Mick West

Staff member
It's an interesting idea, and it might even work over a relatively short distance like 5 miles if it was done accurately.

The most important consideration would be to rise above the near-water refraction. You would want the drone as high as possible while still being above to measure its own height. Also do it when the air temperature is a close to the water temperature as it is likely to get.

You'd want it flown by computer if possible. Probably the simplest way of doing the experiment would be to program it to fly a point to point course towards the camera while maintaining a fixed altitude above the water (the same altitude as the camera).

A calm lake would work best.

For measuring altiutude, a lot of drones have ultrasonic sensors just for that reason. If you were being especially ambitious your could roll your own. This one is accurate to 10m in a resolution of 1mm
https://www.maxbotix.com/Ultrasonic...ed=1&max_range=10m&resolution=1mm&outputs=ttl

The key deliverable would be a video synchronized with data from the drone: 3D GPS coordinates, barometer altitude, and ultrasonic altitude. The altitude would remain stable, and you would see the drone rise up.

Keeping the drone centered in the camera would also be compelling.

On to the point of measuring height; I'm thinking a simple plum line hanging from the drone with a highly visible weight on the end would at least indicate if the water surface was dropping away from the crosshair height

It would be hard to fly with a plumb line, dragging behind, and hitting the waves. However this would work well if you just wanted to make a series of spot observations. The boat could start 5 miles out, and stop over 0.5 miles, and send up the drone to hover at plumb-line height.

#### cloudspotter

##### Senior Member.
It would be hard to fly with a plumb line, dragging behind, and hitting the waves. However this would work well if you just wanted to make a series of spot observations. The boat could start 5 miles out, and stop over 0.5 miles, and send up the drone to hover at plumb-line height.

Yeah, I was thinking spot checking rather than dragging

#### Rory

##### Senior Member.
Seems like a good experiment to propose to flat earthers, for them to carry out themselves.

Though if they don't trust theodolites...

#### Bunkmeister

##### New Member
I like the idea, but it might be easier to get up a hill or a tower that has a view of a fixed land object of identical height several miles away. There is less wiggle room then to debate or question any altitudes.

#### Mick West

Staff member
I like the idea, but it might be easier to get up a hill or a tower that has a view of a fixed land object of identical height several miles away. There is less wiggle room then to debate or question any altitudes.

A single fixed observation is open to "alternative" interpretation. The benefit of the drone suggestion is that it provides a series of data points which, when plotted on a graph, will form a curve.

#### jarlrmai

##### Senior Member
Drones also have altimeters and self regulate to the same altitude.

#### Mick West

Staff member
Drones also have altimeters and self regulate to the same altitude.

Altimeters are devices designed to calculate the height of an aircraft above the surface directly below it. This height may be Above Ground Level (AGL) or Above Sea Level (ASL).

Different types of altimeter use different technologies to calculate this height, including pressure-density to altitude relationship and the propagation and reflection of electromagnetic waves etc.

There are four main types of altimeter:

• Barometric altimeter.
• GNSS (GPS, Galileo, etc).
• Laser altimeter.
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What is wanted specifically here is a physical measure of the distance to the surface of the water (preferably a lake). So of the four methods listed above, only the Radio and Laser Altimeter would work. It might be a bit fiddly over water, with reflections.

There's also ultrasonic, which only works for a limited range (like 10m, 30 feet), so is not really considered an altimeter, more of a landing aid. But might be the best bet here.

Of course, the ideal thing is to have ALL the data, GPS, etc, and plot them all together.

#### jarlrmai

##### Senior Member
Okay I get it so the drone corrects altitude to the fixed point but the ground drops away with the curvature of the earth and this is measured with the altimeter.

#### Trailblazer

##### Moderator
Staff member
I think it would be difficult to keep the drone centred in the theodolite. It would be easy to have it maintain a fixed altitude above the sea, but that would of course result in it dropping below the crosshairs as it went away. You'd need some pretty skillful flying.

#### Mick West

Staff member
I think it would be difficult to keep the drone centred in the theodolite. It would be easy to have it maintain a fixed altitude above the sea, but that would of course result in it dropping below the crosshairs as it went away. You'd need some pretty skillful flying.

I was thinking that too could be automated - a computer flying the drone remotely to keep it in the middle of the video image.