I think its a known problem about artoolkit .. this link Robust Pose estimation from planar target mentions some of those..
Steven,
I'm not sure if this is exactly the problem you are observing, but I
have noticed a similar behavior from ARToolkit before. When the camera
is nearly perpendicular to the marker, and the marker is in the center
of the image, there occurs a singularity. Let's say the angle between
the marker normal and the optical axis is 1 degree - ARToolkit will
arbitrary flip between +1 and -1 degrees. If you make the angle
bigger, the orientation of the marker becomes less ambiguous, and the
error diminishes.
Ivan Dryanovski
On Mon, Nov 8, 2010 at 9:00 AM, Herman Bruyninckx
<Herman.Bruyninckx@mech.kuleuven.be> wrote:
> On Mon, 8 Nov 2010, Steven Bellens wrote:
>
>> 2010/11/8 Steven Bellens <steven.bellens@mech.kuleuven.be>:
>>> Hi,
>>>
>>> I'm experimenting a bit with the ar_pose package. I'm using a single
>>> fixed camera to track a moving marker. To verify the estimation
>>> accuracy, I just leave the marker fixed and I've plotted position and
>>> orientation estimates. The position estimates are pretty much
>>> constant, but the orientation estimates are oscilating a lot (see
>>> appendix), and apparently always between two values. Is this because
>>> of the bad capability to estimate that orientation or can this be
>>> caused by the environment conditions (light - set-up - distance to
>>> marker)?
>>
>> For clarity, plotted are the 4 components of a unit quaternion.
>
> So...? What does a jump of "0.1" quaternion units mean? And is this meaning
> the same for each of the four components?
>
> The answer to this last question is probably "no", hence...?
>
> Herman
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