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Author Topic: Noisy data  (Read 2225 times)

janoz

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Noisy data
« on: January 14, 2015, 06:01:56 PM »
Recently i have serious problem when documenting flat surfaces - like flat facades covered by fine plaster. Regardless of number of photos and photo setting (i always use ISO lower than 200 and  never higher) i always get big noise on flat areas. On parts of roofs , for instance, there is no problem with the same photo data. This occures only on flat walls with plaster. If a wall  is in "raw" rock material there is no problem. Problem is visible already on sparse pointcloud, where on flat areas only the border lines of particular plaster color borders are visible whereas on roof the density of points is sufficient. It seems to me that the SW cannot determine neccessary amount of tie and image specific points on flat one colour areas. But on the other hand i have seen posts where the guys were able to generate very smooth dense clouds on car models so there must be some solution..... By the way the alignment is always OK

Photogrammetryfacts

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Re: Noisy data
« Reply #1 on: January 14, 2015, 10:10:45 PM »
I have som (very limited) data that seems to suggest that lower ISO isn't always the best with photogrammetry. In my case with my DSLR I seem to get more points when I use iso 400 compared to 200.

As for your problem, you may want to try to process a copy of your raw data files and bump the contrast as far as it will go. This will hopefully give you a little more contrast in the areas you struggle with now and help photoscan detect more points. Simply change the pictures to the unprocessed ones when generating the texture.

Also make sure the plaster wall isn't overexposed, but I assume it's not.