How Do I Use The Camera to Estimate the Height of an Object?

[JAW]

Here's the situation----There's a clump of trees in an otherwise open area where I often take off. I would like to know how high the tallest tree is. I could hover at what appears to be the top of the tree by centering its image on the screen and referring to the altitude readout, but unless the camera is pointing straight ahead and (more importantly) parallel to the ground, the readout would not be accurate. Is there a command in Go4 or Lichi which centers the camera so that it is pointing straight ahead and parallel to the ground?
TIA!

 

[THE CYBORG]

You could always use a little trigonometry

 

[Mr. Salty]

Yes, the slider on the right side of the screen that controls the gimbal shows you the degree of tilt for the camera.

 

[johnmeyer]

There is a command, which you can assign to one of the buttons, which alternates the gimbal between pointing straight down, and straight ahead. When it returns to straight ahead, it is not only at zero degrees vertically, but is also centered horizontally, in case you have "swiped" the gimbal from one side to the other, using your finger.

So use that and you will have exactly what you want.

 

[JAW]

There is a command, which you can assign to one of the buttons, which alternates the gimbal between pointing straight down, and straight ahead. When it returns to straight ahead, it is not only at zero degrees vertically, but is also centered horizontally, in case you have "swiped" the gimbal from one side to the other, using your finger.

So use that and you will have exactly what you want.

Having some difficulty locating that option. I'm running Android on a CrystalSky

 

[sdold]

One method I use is to line up the top of the tree with the horizon.

 

[FlyGuy8675309]

I hate to point out the obvious, but why don't you just use your eyes to lower the drone to just above the highest tree instead of using the camera?

 

[sdold]

I hate to point out the obvious, but why don't you just use your eyes to lower the drone to just above the highest tree instead of using the camera?

It can be hard to tell when you're looking up at an angle. The OP has the right idea using a camera, but I don't know how the height reporting from the drone can have the kind of accuracy he seems to want.

 

[johnmeyer]

Having some difficulty locating that option. I'm running Android on a CrystalSky

I just realized that I don't know what drone you are flying. Mine is a Mavic 2 Pro and it has this option in several places and is easy to find in the manual.

 

[FlyGuy8675309]

It can be hard to tell when you're looking up at an angle. The OP has the right idea using a camera, but I don't know how the height reporting from the drone can have the kind of accuracy he seems to want.

He used the word "estimate", so I'm assuming being with a few feet is OK. I've used the hover-and-lower method to gauge the height of obstacles for a while. IMHO it's much safer to use your eyes rather than using the camera to perform tasks like this.

 

[sdold]

I must be missing something. All he needs to do is center the horizon on-screen using the tilt control.

 

[sar104]

I must be missing something. All he needs to do is center the horizon on-screen using the tilt control.

Provided there is a true horizon. There might be mountains. Or he might be on the edge of the earth...

 

[Bigbird48]

why not just get directly over top of the object and lower the drone till the sensors stop it and subtract that from the overall height.

 

[JAW]

I hate to point out the obvious, but why don't you just use your eyes to lower the drone to just above the highest tree instead of using the camera?

Were that true in my case, I wouldn't be taking up bandwidth with the question in the first place. I was never very good at visual trig.

 

[Bigbird48]

Were that true in my case, I wouldn't be taking up bandwidth with the question in the first place. I was never very good at visual trig.

go above the object point cam straight down use the screen on your phone or tablet to see with and lower the drone till it stops from the sensors that will give you the height of the object plus what is it 3.9 ft I think. Or point the cam straight go out to the side of the object and using the screen move up or down till your even with the top of it. Its not that hard

 

[AMann]

Theodolite Augmented Reality Viewfinder for iPhone and iPad

 

[sdold]

Provided there is a true horizon. There might be mountains. Or he might be on the edge of the earth...

That's true. There is one other method that should provide the accuracy the OP needs. He could use the camera to sight down the edge of a bubble level. It means he'd have one more thing to carry, but it could double as a walking stick.

 

[JAW]

tough crowd

 

[FlyGuy8675309]

Were that true in my case, I wouldn't be taking up bandwidth with the question in the first place. I was never very good at visual trig.

???? Visual trig? All you need to do is... ..nevermind. Best you climb to the top and drop a long tape measure down.

 

[johnmeyer]

tough crowd

... and a tough OP. You've gotten a lot of decent suggestions but have rejected them all. I gave you a suggestion of how to center the gimbal and then when I asked what drone you are flying, in order to know if the centering I mentioned could be done on your drone, you never replied.