[ros-users] Hokuyo intensity values

[Abe Bachrach]

Cool, thanks for the info!
At this point, not entirely sure what we'll use it for, but thought it might
be useful, and we should at least be logging the info.

-=Abe

On Wed, Apr 14, 2010 at 11:34 AM, Radu Bogdan Rusu <rusu at willowgarage.com>wrote:

> I concur with what Vijay said. The intensity data was used for extracting
> the door handle using statistical methods.
>
> Regarding intensity calibration, there's work mostly done by our colleagues
> in photogrammetry and sensing
> (http://www.gc.vgtu.lt/upload/geod_zurn/gc_vol35_no3_77-81_vain.pdf for
> example).
>
> Cheers,
> Radu.
>
> Vijay Pradeep wrote:
> > Hi Abe,
> >
> > It's great to hear that you're interested in using Hokuyo intensity
> > data.  I'm not certain as to how much intensity data is being used in
> > our point cloud processing pipelines.  I think intensity might be used
> > in our door handle detector.  Someone else can elaborate further on this.
> >
> > Intensity data is a critical part of the pr2_calibration stack.  We use
> > intensity images (just like what was on the
> > 'Scanner_to_camera_calibration' page) to extract checkerboard corners,
> > which is the first step in a much larger full system calibration
> procedure.
> >
> > /it seems that the values are normally somewhere between 0 and 6000.
> > However every once in a while, they'll go as high as ~15000./
> > I can agree with the 0-6000 intensity estimate, but I've definitely also
> > seen spurious bright returns.  I haven't really paid attention to how
> > large these returns get (maybe they are in fact ~15000), but I have
> > noticed that the spurious bright returns occur most often when rays
> > glance off the edges of objects.
> >
> > /it says that the intensity is a function of distance... is there a good
> > way to normalise out the distance factor so that intensity values can be
> > compared on a normalised 0 to 1 range?
> > /I don't believe anyone here has tried to build an intensity/range
> > model, probably because we don't have a strong use case for this type of
> > normalization.  Somewhat related, I'd be curious to see how intensity
> > data could be used to compensate for range biases.
> >
> > I'm definitely interested in hearing how you end up using the intensity
> > data!
> >
> > Vijay
> >
> > On Tue, Apr 13, 2010 at 4:57 PM, Abe Bachrach <abachrach at gmail.com
> > <mailto:abachrach at gmail.com>> wrote:
> >
> >     Hi there,
> >     I started looking at the intensity values that you can get from the
> >     hokuyo UTM laser scanners, but was seeing a much wider fluctuation
> >     in the values than I would have expected...
> >     from looking at my own data, and the data posted on the calibration
> wiki
> >     http://pr.willowgarage.com/wiki/Scanner_to_camera_calibration
> >
> >     it seems that the values are normally somewhere between 0 and 6000.
> >     However every once in a while, they'll go as high as ~15000.
> >
> >     In the documentation posted here:
> >
> http://www.ros.org/wiki/hokuyo_node?action=AttachFile&do=get&target=UTM-30LX_Specification.pdf
> >     <
> http://www.ros.org/wiki/hokuyo_node?action=AttachFile&do=get&target=UTM-30LX_Specification.pdf
> >
> >     it says that the intensity is a function of distance... is there a
> >     good way to normalise out the distance factor so that intensity
> >     values can be compared on a normalised 0 to 1 range?
> >
> >     How have you guys generally worked with the intensity info.
> >
> >     thanks in advance!
> >     -=Abe
> >
> >
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> >
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> --
> | Radu Bogdan Rusu | http://rbrusu.com/
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