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Author Topic: Accuracy of Point Cloud Changed?  (Read 4476 times)

tdepke

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Accuracy of Point Cloud Changed?
« on: November 16, 2011, 02:42:19 PM »
I am running on a computer that has little local space on the hard drive so I've been going back and forth from a network drive to the local drive. I ran the same exact chunk in the same exact file with one file location on the local drive and another on the network drive because I just wanted to test performance for Aligning photos (I also ran a Build Geometry yesterday that took 20+ hrs on the network drive when it used to take about 12 on the local). The RMSE for my GCPs was significantly different between the two files...this seems super weird.

Screen shots of the two GCP windows are attached.

Alexey Pasumansky

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Re: Accuracy of Point Cloud Changed?
« Reply #1 on: November 16, 2011, 03:06:03 PM »
Hello Tyler,

Align Photos step could produce slightly different results.

The difference in the Error column could be considerable if you process for example one line of aerial photos that have only one-dimensional overlapping. If the set of data has overlapping in two dimensions the values in the error column would not vary much while performing align photos.
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Alexey Pasumansky,
Agisoft LLC

tdepke

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Re: Accuracy of Point Cloud Changed?
« Reply #2 on: November 16, 2011, 03:55:53 PM »
Yes, that would make sense Alexey. I think I didn't explain myself correctly. What I am saying here is that I was doing the exact same "align photos" step for the exact same photos in the exact same project, but I ended up getting different results. I saved a project on two different hard drives, one of the files was on a network drive, and another was on a local drive and when I performed this analysis on each file, the accuracies were slightly different.

Could it be the way that the .jpg files are stored on an HD or something like that?

Alexey Pasumansky

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Re: Accuracy of Point Cloud Changed?
« Reply #3 on: November 16, 2011, 04:06:38 PM »
Quote
What I am saying here is that I was doing the exact same "align photos" step for the exact same photos in the exact same project, but I ended up getting different results.

Yes, it is possible. Due to some uncertainties you can get a little bit different result even re-aligning the same set in the same PhotoScan session. The value of the possible difference mostly depends on the positions of the images in the data-set.
Best regards,
Alexey Pasumansky,
Agisoft LLC