Sudhir

Stitching of oblique images for 3D model of trees

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Hello Everyone,

Sudhir is here...from many days I have been facing problem of building 3D model of plants for taking overall structure of plant .

Below I have mentioned strategy for the project :

1. All plants are planted in parallel rows having height of 4-5 ft from ground surface.

2. Data is captured by using MAPIR survey 3W (RGB) camera attached  obliquely to UAV at an angle of 30 degree

 

I have taken some of flights at following methods :

 Parallel to the row plants ( oblique at 30 degree)

80-80 % side &  front overlap with Mission planner software

7 m above the ground level

 

II. Cross grid flight  (oblique at 30 degree)

80-80 % side &   front overlap with Mission planner software

7 m above the ground level

 

III. Parallel and perpendicular to the row of plants (Nadir view)

80-80 % side &  front overlap with Mission planner software

7 m above the ground level

 

I have tried all kinds combination for building 3D model but still I'm not able to find solution for it.

Kindly suggest weather I'm making mistake while capturing data for the above objective or any workflow in agisoft that I'm not able to reach.

Thank you!

 

Regards

Sudhir

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Everyone thinks the key to photogrammetry is shooting obliques and the amount of overlap.  Keep in mind that this is called PHOTOGRAMMETRY so the most important thing is your understanding of photography.  

Secondly is the software you use.  There are predominantly two types of 3D reconstruction, one for mapping and survey and the other for 3D Models. Generally the software will work for both, but one is optimized for planar - NADIR, the other for surfaces - obliques.  I have not used Agisoft, but things like DroneDeploy and Px4D are very limited with obliques. 

Here’s a sample of what we do in ContextCapture.  Best viewed on a desktop. 

http://162.144.22.103/models/Transformers/#%2F

We use a Sony A7RIII, the lens and angle depend on altitude and FOV.  These substations are energized so we usually fly around 100+ feet and fly 7m/sec.  The key to a good model is not the overlap but the number of different angles you get in your coverage.  We fly a combination of grid and orbits and for this level of detail we shoot approximately 5000-12000 shots depending on the size of asset.  This model is a smaller piece of an eight acre facility.  

We consider substations to be fairly high frequency, lots of occlusion, but nothing compared to trees.  I’m not familiar with your camera, but the higher the frequency the better the resolution, lighting and exposure need to be.   Again, the collection of data is all about the photography.  You can’t model what you can’t see and the sharper the image the better the model, motion blur has a very negative effect on the model.  We never shoot below 1/800 so exposure can sometimes be a challenge.  

If the trees are dense then you need to capture it with A lot more angles, time permitting we will also shoot from different altitudes and focal lengths.  Depending on the software you can’t go from 140 feet with a 50mm lens to 100 feet with 16mm lens, but changing it up adds more angles which helps build a better model.  You’ll have to experiment with your setup to determine the right technique.  

Good luck, if this is your first attempt at Photogrammetry you certainly picked one of the harder things to model.  Let us know how it goes.

 

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@Av8Chuck

great info and insight. I am new to the whole idea of 3D Mapping/Modeling and since it is strictly for Hobby I am not willing to pay the big bucks for the more reliable commercial products. I have been spending a great deal of time with Meshroom and getting finally to a point where I can create a 3D model of a home or a building. 

I am not pleased with the quality so far but that has to be the actual pictures I am taking and like you said the angles.

 

the biggest issues seem to be the number of pictures, it seems to be quantity vs quality. Just because I take 1500 pictures and it takes 12 hours to process does not mean I am going to end up with a 10 times better model if I would have only taken 150 pictures.

i am currently using the new DJI Mavic 2 Pro. But having no photo experience and I mean none at all, the whole ISO or even FOV stuff has me scratching my head. Things I have learned are

-try to keep the sky out of the frame

- cloudy days are best

- Shinny/gloss things don’t expose well. Like water or black/white cars. White roofs or snow are killers as well

bottom line is finding a way for us beginners to set our cameras to the right settings would be very helpful, is there a tool or an article that has good examples to assist??

Also where to share our finished model,every model I have created of a house or a building are over 100 MB, so places like Sketchfab will not work (max 50mb). Like I said it is a hobby and I end up with something I think is pretty cool, but only I am able to see it.

ANY IDEAS ON ANY OF THIS??

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