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3D model artifacts and dropped images

Hi MME,

I processed a set of 216 images with 90% front and side overlap of an island in a clear lake.  I understand there are no guarantees, given that there is so much water in these photos, but MME did quite well!

In "Rhody Island 2" MME did well with the stitching, despite dropping 30 photos.  The resulting .las looks very good when viewed with Quick Terrain Reader.  However, the orthomosaic, DEM, and obj/texture (uploaded to SketchFab) all show strange linear artifacts from the tops of the trees and ramping down to the west. 

I thought this could potentially be fixed by processing in "Full 3D" so I submitted again.

In "Rhody Island 3" the artifacts ramping down to the west are gone, which is great.  But nearly half of the images got dropped.

Can you please comment/advise on the following:

1. Why, in Rhody Island 2, do the western ramping artifacts exist in the obj, dem, and ortho, but not in the .las?

2. Why, in Rhody Island 3, did so many photos get dropped?  Was it just because of the water?  They weren't all dropped when "Full 3D" was unchecked, so I was a bit surprised to see them get dropped when Full 3D was checked.  Is there anything I can do to reduce the images from being dropped (color correction, increased contrast, etc.)?

 

Thanks for any insight you can provide.

-Nick Wagner

n.wagner124@gmail.com

N Wagner124

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We were actually looking at this job just because the water was so clear. 

1. When you are around water like this it can make the model do a lot of weird stuff. You actually had quite a few reflections in the images and I am surprised it turned out as well as it did. Almost every image had a sun glare in it. 

2. Full 3D processing is definitely not what to use here. It is very aggressive with its filtering in an attempt to clear up overhanging areas. 

Any time you are mapping around water you should use a circular polarizing filter to block some of the glare and increase contrast. 

You would likely be better off mapping either earlier or later in the day to get the sun glare out of the camera's field of view. Or a cloudy day but that wouldn't look as cool.

 

Zane
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Thanks Zane.  I just ordered a circular polarizing filter!

Can you help me understand why in Rhody Island 2, the .las differs from the .obj and DEM with respect to the sloping artifacts?  If the .las more correctly represents the true 3D model, why can't the obj and DEM also reflect that better representation?  I want to understand so I can know what to expect between these different outputs in the future.

Thanks,

-Nick 

N Wagner124 0 votes
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The LAS operates just off the points that are found. The DEM gets created from those points but has a plane that gets set. In this case the plane was rotated because of all the weird points from the water and you get the weird tilting. 

Zane 0 votes
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