[OpenDroneMap-users] "bowl" effect

[Stephen Mather]

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





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