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Author Topic: Strange Artifacts in Models  (Read 6156 times)

sarko

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Strange Artifacts in Models
« on: September 14, 2011, 06:34:21 AM »
Hello,

I have been trying to resolve a strange problem that I am having.  I have used Photoscan Pro successfully on many sets of aerial photography, but recently have been having a problem.  I have a set of older aerial photos (1949-era) that I am trying to generate a DSM from.  I import and align the images and all looks fine.  They generate a good number of points and the alignment seems to work properly.  When I try to build the model, however, I get the following result,


If I try to change parameters (high vs. medium alignment or low vs. medium on model build) I can sometimes get a better result, but often it has this problem.  Then some runs will just work and it will look good.  It is a very strange issue and I'm wondering if others have seen it.  Perhaps I am setting up my project wrong, but I have run many other data sets without this problem. 

Thanks,
Scott

Alexey Pasumansky

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Re: Strange Artifacts in Models
« Reply #1 on: September 14, 2011, 03:03:59 PM »
Hello Scott,

Thank you for reporting. We've sent you the e-mail for more details.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Matt

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Re: Strange Artifacts in Models
« Reply #2 on: September 21, 2011, 07:44:36 AM »
Hi Scott,

I dont get the strange artefacts you are but have noticed irregularities in models derived from scans of old prints.  The old prints seem to bleed and and have inconsistent tones in the whites and light greys and as such generate very undulating surfaces in areas of flat terrain. Looking at your aerials i would mask out the corners of the photos as they are darkened substantially and photoscan doest seem to deal so well with high contasts between the same spot on different photos. Are you aligning the old aerial photos prioir to use in photoscan (lining up fiducials/interior orientation) as this increases accuracy substantially.

Matt

 

sarko

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Re: Strange Artifacts in Models
« Reply #3 on: October 26, 2011, 01:25:19 AM »
Hello,

Just to follow up on my original post, I think I may have finally identified what is going on here and it may relate to PhotoScan directly.  The artifacts in my model appear to be due to using OpenCL on a newer MacBook Pro.  I have a MacBook Pro i7 with 8GB of RAM and the ATI Radeon HD 6750M graphics card.  When I enable PhotoScan to use the OpenCL device, I get the artifacts throughout my model.  When I disable this device I get clean models with no artifacts at all.  No other changes in parameters, just disabling the OpenCL device.  I have now tested this on a couple data sets with and without OpenCL and it seems to be consistent.  Same problem exists in PhotoScan Pro 0.8.3 and 0.8.4.

Thanks,
Scott