[OpenDroneMap-users] Newbie focal length override

[Stephen Mather]

Hi Howard,

Digging deeper: try '--force-ccd' but only after distortion correction:

My read of things is that Alex Mandel's lencorrection script won't work
with GoPro3 (unless they are the same...), until Lensfun supports it:
http://wilson.bronger.org/lensfun_coverage.html . The nice thing is this is
a good pre-processing step for all sorts of other lenses, with just the
change of the
https://github.com/wildintellect/lenscorrection/blob/master/gopro.xml (Alex
is on the list, so he can speak with more authority). Also, it's nice that
Alex' script writes a custom EXIF entry in the header, which could be added
to the ccd_list.json in a pinch.

Solem's vision blog may be your simplest solution at the moment, just make
sure your calibration shots of the checkerboard pattern is in the same
video mode as your data are collected, so that you are using the same
portion of the CCD for each (I think this matters...).

I hope that I'll be working on this soon for our own images from the GoPro3.

Cheers,
Best,
Steve



On Sun, May 10, 2015 at 6:27 PM, Stephen Mather <stephen at smathermather.com>
wrote:

> Hi Howard,
>
> Welcome! Try forcing the ccd size. Did you do any barrel distortion
> correction first? This is something ODM doesn't do well (yet) as it only
> does 3-parameter (not 6-parameter) distortion corrections. This is
> something that needs worked into the toolchain in the near future.
>
> References:
>
> There's a calibration class up here from Cole:
> https://github.com/colek42/TrackIt/blob/master/catkin/src/stabilize/src/calibrate.py
>
> plus Alex' work here (GoPro2 only, but a good example):
> https://github.com/wildintellect/lenscorrection
>
> Finally, see Jan Erik Solem's work here for a full calibration solution:
>
> http://www.janeriksolem.net/2014/05/how-to-calibrate-camera-with-opencv-and.html
>
> Once you've done the correction and cropped, you'll need to estimate the
> ccd size of the cropped area, I think, and then it should feed in just fine.
>
> Cheers,
> Best,
> Steve
>
>
>
>
>
> On Sun, May 10, 2015 at 1:20 PM, Howard Butler <howard at hobu.co> wrote:
>
>> All,
>>
>> So I have a 2 min 720 video from a GoPro Hero 3 Black that I ripped out
>> 126 images out of using ffmpeg. I want to attempt to start with that.
>>
>> When I attempt to run them, I get the following error:
>>
>> > no CCD width or focal length found for image-100.jpg - camera: “ "
>>
>> Of course this is a FAQ, but my pattern isn’t quite the same. If I try
>> —force-focal 5.76, which is the GoPro entry in the json file, it still
>> blows up.
>>
>> Ideas?
>>
>> Thanks,
>>
>> Howard
>> _______________________________________________
>> OpenDroneMap-users mailing list
>> OpenDroneMap-users at lists.osgeo.org
>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/opendronemap-users
>>
>
>
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