[ros-users] ar_pose orientation accuracy

[Eohan George]

I think its a known problem about artoolkit .. this link Robust Pose
estimation from planar
target<http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.64.3894&rep=rep1&type=pdf>
mentions
some of those..
The artoolkitplus has a robust pose estimate api which "reduces" this
problem. However, I did see this issue to a smaller extent even with rpp. I
am not sure if I was using it the wrong way though.

Eohan

On Mon, Nov 8, 2010 at 10:47 AM, Ivan Dryanovski
<ivan.dryanovski at gmail.com>wrote:

> 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 at mech.kuleuven.be> wrote:
> > On Mon, 8 Nov 2010, Steven Bellens wrote:
> >
> >> 2010/11/8 Steven Bellens <steven.bellens at 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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