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Author Topic: import camera externals  (Read 3464 times)

Twister

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import camera externals
« on: August 09, 2015, 06:00:06 PM »
Dear PhotoScan team,

small objects are often measured with a stationary camera, while moving the object on a turntable or a 2-axis gimbal. With a stepper motor under computer control, this motion can be highly reproducible, which offers the possibility to locate the "camera positions" (with respect to the object) with optimum accuracy using a large and cooperative calibration target, and to re-import the information into PhotoScan. 

To my knowledge, this is now only possible for the positions X, Y, Z, but not for the camera orientations Roll, Pitch and Yaw. With the complete externals from a calibration, and assuming this data to be exact, one should be able to skip the whole alignment step, offering these advantages:
- saving of time
- better results for objects seen under a small angle (smaller than the calibration target) from the camera
- setting a calibrated reference coordinate system if the target includes a known distance.

Best regards,

Twister

Alexey Pasumansky

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Re: import camera externals
« Reply #1 on: August 09, 2015, 06:08:13 PM »
Hello Twister,

Alignment step that includes estimation of the camera extrinsic and intrinsic orientation is only possible, if the mentioned data is present. So if you can provide precise parameters for camera positions/orientations and also information on the calibration/distortion data, then you can adopt this data for one of the supported formats of the Import Cameras option.

However, I'm not sure how precisely the rotations of the turntable can be reproduced, as even small inaccuracies will result in the alignment failure.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Twister

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Re: import camera externals
« Reply #2 on: August 09, 2015, 10:37:22 PM »
Hello Alexey,

thank you for your fast reply!

You are right, besides the external parameters the internals, including distortion, must be available, which is the case.

I will check out the repeatability of the calibration with a large and cooperative target ("good object"). But I think that, even with some degree of reproducability errors of the computerized rig, the results using the target data should be better than an alignment solely on the base of a small or weekly texturized sample ("bad object").

Best regards

Twister

Paulo

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Re: import camera externals
« Reply #3 on: August 10, 2015, 05:17:17 PM »
Hello Alexei,

It would be great if in the Import Cameras format options, Inpho format would be available as it would be very useful!

I would be then be able to import Cameras internals and externals from an Inpho project!

Thnks 
Best Regards,
Paul Pelletier,
Surveyor