[OpenDroneMap-users] "bowl" effect

[Anna Petrášová]

On Mon, Oct 5, 2015 at 10:27 PM, Stephen Mather <stephen at smathermather.com>
wrote:

> Hi Anna,
>
> Good news. I've been bad here and cc'd Pau who an hopefully answer your
> question on parameters.
>

I found this function in OpenSfM:
https://github.com/mapillary/OpenSfM/blob/master/opensfm/exif.py#L50

which undistorts a gopro  camera, so I guess I can inject my values there
(not tested yet)

>
> That said, if you have all the parameters, is there any reason to not
> undistort before feeding into ODM?
>

True, what would be the simplest way to do that? But then how do you tell
ODM to not try to undistort the pictures again? During the processing with
opensfm, I can see:

running "/odm_app/OpenDroneMap/bin/RadialUndistort"
"/vagrant_data/June19_subset/reconstruction-with-image-size-2402/list.txt"
opensfm/bundle_r000.out pmvs
[ReadBundleFile] Bundle version: 0.300
[ReadBundleFile] Reading 126 images and 49430 points...
Undistorting image ./dsc01522.jpg
Undistorting image ./dsc01523.jpg
Undistorting image ./dsc01524.jpg
Undistorting image ./dsc01525.jpg

Sorry if I am missing something


Best,

Anna


> Cheers,
> Best,
> Steve
>
>
>
>
> On Sun, Oct 4, 2015 at 6:04 PM, Anna Petrášová <kratochanna at gmail.com>
> wrote:
>
>>
>> On Thu, Jun 25, 2015 at 11:04 PM, Stephen Mather <
>> stephen at smathermather.com> wrote:
>>
>>> If memory serves, Anna has proper survey points, so Z is pretty good.
>>>
>>> Regarding the alternate branch -- there's nothing wrong with it, and
>>> it may be the FUTURE, but TBH, I haven't had a chance to test it
>>> properly... . I was hoping you'd try it, since you have such good
>>> secondary data to verify how it does... .
>>>
>>> Cheers,
>>> Best,
>>> Steve
>>>
>>>
>>>
>>
>> Hi,
>>
>> finally tested the OpenSfM now when it's merged. It gives better results
>> in terms of the bowl effect - there is still some, but not as huge (and it
>> seems faster). Does anyone know if I can pass calibration parameters of the
>> camera to OpenSfM? In the configuration file, there is:
>>
>> radial_distorsion_k1_sd: 0.01 # The standard deviation of the first
>> radial distortion parameter (mean assumed to be 0)
>>
>> but I have k1, not its standard deviation? Should I rather ask on the
>> mapillary forum?
>>
>> Thanks,
>>
>> Anna
>>
>>
>>>
>>>
>>>
>>> On Wed, Jun 24, 2015 at 2:20 AM, Alex Mandel <tech_dev at wildintellect.com>
>>> wrote:
>>> > On 06/22/2015 06:24 PM, Anna Petrášová wrote:
>>> >> On Mon, Jun 22, 2015 at 6:00 PM, Stephen Mather <
>>> stephen at smathermather.com>
>>> >> wrote:
>>> >>
>>> >>> Ah, ugly. Well, pretty really, but ugly from a data perspective. So
>>> >>> systematic bias in structure from motion is an issue with all
>>> systems, and
>>> >>> difficult to overcome with drone imagery in particular, if the drone
>>> is
>>> >>> flown in a single Z plane, particularly over relatively flat
>>> terrain.  This
>>> >>> is an indictment of the data, just stating a known difficulty. This
>>> is why
>>> >>> balloon and kite flights, aside from areal coverage, are so pleasant
>>> to
>>> >>> process -- plenty of x, y, and z movement, so less chance for
>>> systematic
>>> >>> bias. I've been wondering if once a dataset like Open Terrain (a
>>> global
>>> >>> highest-available) is available, if it might be helpful for
>>> compensating
>>> >>> for bias in datasets, and also help with data classification
>>> pipelines that
>>> >>> can have separate meshing mechanisms for ground, vegetation, and
>>> human
>>> >>> structures.
>>> >>>
>>> >>
>>> >> I was thinking about compensating for the bias based on the lidar
>>> data I
>>> >> have, but I haven't tried it yet.
>>> >>
>>> >>>
>>> >>> That said, let's get a little more context on the dataset and
>>> processing
>>> >>> -- did you use ground control and if so, how was it distributed? It
>>> would
>>> >>> be interesting to know if you had ground control in the center of the
>>> >>> scene, if ODM is ignoring this extra info. Also, what kind of camera
>>> is it?
>>> >>> It is possible that the three parameter corrections that ODM is
>>> performing
>>> >>> are inadequate, and a 6-parameter model would be better.
>>> >>>
>>> >>
>>> >> There isn't really any gcp in the middle of it:
>>> >>
>>> https://drive.google.com/file/d/0B7CQoT4YE2mMNzJSbEZsaGtrZ3hnRUdPQ3VDbF9DS0o2SS1j/view?usp=sharing
>>> >>
>>> >> but how could the GCPs help? Georeferencing won't really change the
>>> shape,
>>> >> isn't it just rotation and translation?
>>> >>
>>> >
>>> > The ODM format for a GCP file is X,Y,Z so yes there is height data if
>>> > you are providing GCPs. Of course if the Z is provided from a standard
>>> > GPS unit that might not be super useful.
>>> >
>>> > -Alex
>>>
>>
>>
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>
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