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Author Topic: Align photos  (Read 9084 times)

Peter

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Align photos
« on: June 09, 2013, 07:36:51 PM »
How much better will the high setting in align photos be compared to low and medium?
What will it make better for my ortophoto if i use high setting?

I cant really se any difference to the results if i use high or low.....

tezen

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Re: Align photos
« Reply #1 on: June 09, 2013, 07:54:11 PM »
For slightly moving (f.e. natural) environment/objects it?s better to choose low or medium while high settings will align the cameras better at static objects (like a house or a momument). At a big amount of pictures (100 and much more) it could take too much time for "high" aligning. "Medium" is the best in most cases - best alignment at short time.

Peter

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Re: Align photos
« Reply #2 on: June 09, 2013, 08:07:30 PM »
Thanks for quick answer!!

I?m currently testing and aligning 470 pic?s taken by UAV @ 150 meters and medium takes quite long time to. I run at low now and it takes about 10-20 min.

But i really cant tell any difference when looking at the orto, low vs medium.....
« Last Edit: June 09, 2013, 08:41:22 PM by Peter Eriksson »

Peter

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Re: Align photos
« Reply #3 on: July 03, 2013, 08:37:04 AM »
Just for test i Aligned at high setting on a pretty big project, flown @ 135m with 80% overlap total of 1460 images.

Processing time for aligment right now 9 hours.

And as i said before, i can noice any difference when aligning on low, med and high.

Does this affect the number of points in point cloud?

Porly

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Re: Align photos
« Reply #4 on: July 03, 2013, 11:06:09 AM »
Hello,

it depends on the terrain, you can compare the results by using Ground Control Points. Lower error shows better alignment result.

Best regards

airmap3d

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Re: Align photos
« Reply #5 on: July 03, 2013, 11:31:27 AM »
Hi Peter,

From what I can see the visual quality of the ortho doesn't really seem to be all that much better, if at all, when produced from a higher setting.  Although I haven't checked the geo-accuracy??

And yes, the sparse point cloud will be much larger when 'high' setting is selected.  If you are only interested in the ortho then you may be able to get away with aligning photos on low but if you are also requiring a point cloud to accurately represent the terrain you should definitely run it on high.

It does take a long time, especially with large amounts of images but that can be easily decreased by investing in some high end computer hardware.  The CPU's are dealing with Gb's of data so to a certain degree, you just have to be patient.  I would recommend dual xeon processors, good ones, if you don't already have that. 

Alexey Pasumansky

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Re: Align photos
« Reply #6 on: July 03, 2013, 01:10:21 PM »
We recommend to pay attention to average value of reprojection error after alignment in case it is more than 0.8 it's better to realign the dataset with higher accuracy parameter.

The processing speed can be improved if pre-selection is used. For big aerial dataset using Ground Control pre-selection is strongly recommended.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Peter

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Re: Align photos
« Reply #7 on: July 04, 2013, 03:01:38 PM »
Hi Peter,

From what I can see the visual quality of the ortho doesn't really seem to be all that much better, if at all, when produced from a higher setting.  Although I haven't checked the geo-accuracy??

And yes, the sparse point cloud will be much larger when 'high' setting is selected.  If you are only interested in the ortho then you may be able to get away with aligning photos on low but if you are also requiring a point cloud to accurately represent the terrain you should definitely run it on high.

It does take a long time, especially with large amounts of images but that can be easily decreased by investing in some high end computer hardware.  The CPU's are dealing with Gb's of data so to a certain degree, you just have to be patient.  I would recommend dual xeon processors, good ones, if you don't already have that.

I use Phenom II X6 1055T and 16 gb ram and a geforce gtx 560 Ti.

I will look into the xenons :)