Hi,

Francois LE COAT writes:
>>> Monocular Depth:
>>>
>>> <https://www.youtube.com/watch?v=34zUDqEzHos>
>>>
>>> A drone flies between the trees of a forest. Thanks to the optical-fl
ow
>>> measured on successive images, the temporal disparity reveals the
>>> forest of trees... We take a reference image, the optical-flow is
>>> measured on two rectified images. Then we change the reference when
>>> the inter-correlation drops below 60%. We can perceive the relief in
>>> depth with a single camera, over time.
>>>
>>> In fact, when we watch images captured by a drone, although there is
>>> only one camera, we often see the relief. This is particularly marked

>>> for trees in a forest. The goal here is to evaluate this relief, with
 a
>>> measurement of "optical-flow", which allows one image to be matched w
ith
>>> another, when they seem to be close (we say they are "correlated").
>>>
>>> We have two eyes, and the methods for measuring visible relief by 
>>> stereoscopy are very developed. Since the beginning of photography,
>>> there were devices like the “stereoscope” which allow
s you to see the
>>> relief with two pictures, naturally. It is possible to measure relief
,
>>> thanks to epipolar geometry, and well-known mathematics. There are ma
ny
>>> measurement methods, very effective and based on human vision.
>>>
>>> When it comes to measuring relief with a single camera, knowledge is
>>> less established. There are 3D cameras, called "RGBD" with a "D" for 

>>> "depth". But how do they work? Is it possible to improve those? What
>>> I am showing here does not require the use of any “artificial
 neural
>>> network”. It is a physical measurement, with a classic algori
thm,
>>> which does not come from A.I. nor a big computer :-)
>>
>> A WEB page was made to illustrate Monocular Depth...
>>
>> <https://hebergement.universite-paris-saclay.fr/lecoat/demoweb/monocul
ar_depth.html> 
>>
>>
>> This is about measuring monocular depth, just as stereoscopic disparit
y
>> is measured. It means quantifying the depth, with images from a single

>> camera. We can see this relief naturally, but it is a matter of
>> measuring it with the optical-flow :-)
> 
> Until now, drone images came from forests in France. The first images
> were obtained in the French Vosges.
> 
> <https://www.youtube.com/watch?v=245yJJrwMQ0> Drone in the forest
> 
> We are now seeing more and more drones in forests outside of France.
> The available image sources are diversifying...

Here is another example of drone in the forest, outside from France:

	<https://www.youtube.com/watch?v=BO_OUFHFzTY> Forest

We also obtained the trajectory in the X-Z plane, of the flight:

<https://sketchfab.com/3d-models/forest-e253ebd61e2a4bd6abcd21ac56f25bae>


These are filtered measurements and it's not ideal computer graphics.

Best regards,

-- 
François LE COAT
<https://eureka.atari.org/>

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