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Author Topic: Problem with big camera calibration  (Read 12809 times)

balyoa

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Problem with big camera calibration
« on: November 16, 2012, 12:54:30 PM »
Hi all,

I am testing PS on a project with a big camera (DMC-1 from Z/I imaging).
I have a calibration certificate with this values :
Virtual Focal Length [mm] : 120
Virtual Sensor Size [Pixel] : 13824 x 7680
Virtual Pixel Size [m] : 12
Virtual Principle Point [mm] : xp = 0.0, yp = 0.0

How to enter this parameters in PS and fix them in the align process ?

Moreover, I have the position of the cameras for each images on a txt file like this :
N : name of image
X : X center of image
Y : Y center of image
Z : Z center of image
O : Omega orientation of image (degrees)
P : Phi orientation of image (degrees)
K : Kappa orientation of image (degrees)

How to enter this parameters and fix them ?

I want to work without add GCP, because my project is already compute with an other photogrammetry software with bundle adjustement.

Thanks in advance for all your answers.

Best regards.

Yoz
« Last Edit: November 16, 2012, 01:05:33 PM by balyoa »

balyoa

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Re: Problem with big camera calibration
« Reply #1 on: November 19, 2012, 11:44:31 PM »
Hi all,

Hum, no answer....  :(    There are non GIS/photogrammetry experts here ?

Photomod know to do it, but it's more complex and more expensive  :-\

Thanks for help.

Regards

fpbv

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Re: Problem with big camera calibration
« Reply #2 on: November 20, 2012, 12:00:36 AM »
Hi Balyoa

I had this same problem a little while ago.
I put those information at Tools-Calibration C?mera
I just have to transform the focal lenght mm to pixels.
I put it manually and then save the data.

balyoa

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Re: Problem with big camera calibration
« Reply #3 on: November 20, 2012, 07:00:42 PM »
Thanks for your answer.

Ok to put those information in camera calibration tool and fix them, but what are the good parameters for my camera ? All the values are in mm, except sensor size.

Secondly, how to import the positions of my images (XYZ, omega, phi, kappa) and how to fix them during the "align photos" step ? The Coordinates of my photos come from a bundle block adjustment software and are very very accurate (some mm) and I want to keep them.

Thanks a lot.

Regards.


fpbv

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Re: Problem with big camera calibration
« Reply #4 on: November 21, 2012, 03:12:41 AM »
Balyoa

You have to put this in a txt file with the imagery name and then load them at ground control.
Regarding the camera values I?ll see here and tell you later.

balyoa

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Re: Problem with big camera calibration
« Reply #5 on: November 21, 2012, 10:49:28 AM »
I have to put cameras positions and orientations as GCP ? It's not very logic ! Moreover, my cameras orientations are in omega/phi/kappa format (degree), and PS import as Yaw/Pitch/Roll format.

I want to fix camera calibration and camera position during alignement.

How to put correct values ? I'm lost in the logic of this software, that seems to be powerfull ....

Thanks.

macsurveyr

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Re: Problem with big camera calibration
« Reply #6 on: November 22, 2012, 12:49:44 AM »
First, if you have not already, go to Tools, Camera Calibration, select all the images and enter 10000 for both fx and fy - that is 120 mm / 0.012 mm
Enter 3840 in cx and 6912 in cy - those values are 7680 / 2 and 13824 / 2

Select Fixed for Calibration mode - make sure you hit Apply

Now go to the Ground Control panel and import the file you have with N, X, Y, Z, O, P, K

Make sure your image names include the file extension or the name won't match.

Under settings in the Ground Control panel set your camera accuracy to 0 if you like, at least for starters.

I would go ahead and do an alignment and use High and preselection of Ground Control.

After alignment, use Gradual Selection and delete selected points, then optimize - repeat until bundle_adjust is around or less than 0.3 or so.

Perhaps loosen the Camera accuracy and see what errors you have - it is a good check on your previous solution. The results will never agree exactly with any other AT result, but the errors should be about the same- again a good check.

If you have a ground control file, import it and have PhotoScan create markers for you. Go visit where the markers are projected to and perhaps even pin them for another check.

If you do mark the control in PhotoScan, uncheck the cameras as control and use only the ground control. Check the errors against what you had before. By then, you will have a pretty good feel for what is going on with PhotoScan

Tom

balyoa

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Re: Problem with big camera calibration
« Reply #7 on: November 22, 2012, 12:47:44 PM »
Thanks Tom,

I have tested quickly with these new steps.
My results are better, but i have some big errors on my GCP's, about 0.2m (3D).

Does Photoscan is making a report of the bundle adjustment ?

I have two others questions :

- Is it possible to make a filter of the points to build a DTM and not a DEM (DSM) ? see here : http://en.wikipedia.org/wiki/Digital_elevation_model

- How to make contour lines with Photoscan ?

Thanks for comments.

Regards.

Alexey Pasumansky

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Re: Problem with big camera calibration
« Reply #8 on: November 22, 2012, 05:11:14 PM »
Hello baloya,

Currently PhotoScan does not support DTM export and has no contour lines functionality.

Best regards,
Alexey Pasumansky,
Agisoft LLC

fpbv

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Re: Problem with big camera calibration
« Reply #9 on: November 22, 2012, 05:51:20 PM »
Thanks for your answer.

Ok to put those information in camera calibration tool and fix them, but what are the good parameters for my camera ? All the values are in mm, except sensor size.

Secondly, how to import the positions of my images (XYZ, omega, phi, kappa) and how to fix them during the "align photos" step ? The Coordinates of my photos come from a bundle block adjustment software and are very very accurate (some mm) and I want to keep them.

Thanks a lot.

Regards.

Balyoa

Which is your GSD? 0.2 meters is very good...

Unfortunaly countour lines is not a option in PS, I would like to have this too... ;D