[ros-users] Clear cells in costmap with max laser range

[Eitan Marder-Eppstein]

Roderick,

Its actually not the costmap that is ignoring max_scan_range values from the
laser, its the laser projector that takes a laser scan and turns it into a
point cloud. The reason for this is that there is no guarantee that
max_scan_range actually corresponds to the laser not seeing anything. It
could be due to min_range, a dark object, or another error condition... all
the laser knows is that it didn't get a return for one reason or another.

With this said, if you want the costmap to assume that error values are OK
to use for clearing, you can write a filter for the laser scan which takes
all the max_range values and sets them to something slightly less than
max_range. Then, you can configure the costmap to use that filtered scan for
clearing operations. I did this on the cart_hackathon sprint that we did
here at Willow, but I can't seem to find the filter I wrote... I think I was
pretty sleep deprived at the time. However, it should be a really easy one
to recreate if you feel compelled.

For documentation on filters see: http://www.ros.org/wiki/filters

For examples of laser filters see: http://www.ros.org/wiki/laser_filters

Hope this helps,

Eitan

On Fri, Jul 16, 2010 at 10:50 AM, Roderick de Nijs
<rsdenijs at lsr.ei.tum.de>wrote:

>  Hi all :)
>
> Costmap2D seems not to "clear" the space around the robot if the laser scan
> range is max. This means, if you put the robot on an open field (no
> obstacles) it will leave *all* the space around it as *unknown*.
> Essentially, if Costmap sees that the scan_range=max_scan_range... it is as
> if it ignores it.
>
> Is there a way to configure the costmap so it wont do this? With the
> GMapping module it does it...
>
> Thanks and have a nice weekend
>
> Roderick de Nijs
>
>
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