[ros-users] Navigation stack: issue about ground plane detection

Eitan Marder-Eppstein eitan at willowgarage.com
Wed Oct 27 18:36:43 UTC 2010


Xiaojun,

As Radu suggested, a bagfile of the problem along with the section of the
launch file where you bring up the ground removal node will probably be the
easiest way to track this down.

Hope all is well,

Eitan

On Wed, Oct 27, 2010 at 12:14 AM, Radu Bogdan Rusu <rusu at willowgarage.com>wrote:

> Xiaojun,
>
> I might be able to help with that until Eitan wakes up (like he ever sleeps
> anyway).
>
> Can you send me the dataset as a BAG/PCD file (1 PointCloud only please)
> and tell me what (and how) nodes are you using
> to filter the data precisely?
>
> Cheers,
> Radu.
>
>
> On 10/27/2010 12:09 PM, clarkwu wrote:
> >
> > Eiten,
> >
> > I did some further test about the ground plane removal on our robot.
> > With the zero position of tilt laser calibrated, now I am able to see
> that
> > before ground removal, cloud points corresponding to the ground are
> located
> > roughly on the horizontal plane, except a few discrete points still left
> on
> > the ground plane after filtering.
> >
> > Another strange issue is that if the "planar_refine" value set to "1" in
> > launch file, the ground removal filter will not only remove the ground,
> but
> > also a large part of points whose z value may be as high as 0.4 meter. I
> > traced back into the source file sac_inc_ground_removal_standalone.cpp
> and
> > found that it's due to the  plane fitting module within subroutine
> > "computePointNormal". The calculation result from this module about the
> > fitted plane seems incorrect. But I can not tell exactly which step
> inside
> > is wrong since I extracted the code within it into a separate file and
> > calculate some sample points, and the result is matching with the that
> from
> > matlab.
> >
> > Please see enclosed screenshots for details and your comments are
> welcome.
> >
> > best regards
> > xiaojun
> >
> >
> >
> > screeshot without planar refinement, the bottom edge of clouds is close
> to
> > the ground plane:
> >
> http://ros-users.122217.n3.nabble.com/file/n1777999/Screenshot_noplanarrefine_0.png
> >
> >
> > screeshot without planar refinement, a few discrete points stay on the
> > ground after removal
> >
> http://ros-users.122217.n3.nabble.com/file/n1777999/Screenshot_noplanarrefine_1.png
> >
> >
> > screenshot with planar refinement, a large part of points on top of
> ground
> > have been removed:
> >
> http://ros-users.122217.n3.nabble.com/file/n1777999/Screenshot_planarrefine_1.png
> >
> >
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