[ros-users] costmap_2d questions

[Eitan Marder-Eppstein]

Jack,

I'm sorry that you haven't found the documentation on the costmap to be
up-to-snuff, though we've tried to put enough information on there to get
people up and running. There aren't other docs besides those that you see
here: http://www.ros.org/wiki/costmap_2d and here:
http://www.ros.org/doc/api/costmap_2d/html/.... so if you've found those,
there's not much else out there besides example code.

I had hoped that the obervation_sources section of the sensor management
parameters documentation (
http://www.ros.org/wiki/costmap_2d#Sensor_management_parameters) would take
care of the distinction between the <name> and <source_name> namespace
distinction, but perhaps that section is unclear? Or was it just lost in the
noise? I can work to make it better or more prominent, but it would be
useful first to know which was the reason for it being so confusing.

You're right in your recollection about max_range readings being treated as
unknown. If you want the costmap to use this information differently, you'll
have to write a laser filter that takes max_range values in your laser scan
and assigns them slightly less than max_range values. When we've done this,
we typically set up one observation_source that only puts marking
information into the costmap that uses the unfiltered scan and one
observation_source that clears obstacle information in the costmap and uses
the filtered scan topic. In this way, we don't put max range hits in as
obstacles, but we do use them to clear obstacles out.

Hopefully this helps, if you have suggestions for specific documentation
that you'd like to see, do let me know. Also, if you'd like to document your
experience getting the costmap up and running standalone in tutorial form on
the wiki, I'd be more than happy to look it over.

Hope all is well,

Eitan

On Fri, Sep 17, 2010 at 9:25 PM, Jack O'Quin <jack.oquin at gmail.com> wrote:

> I am experimenting with costmap_2d to do sensor fusion for our
> autonomous vehicle. I expect to end up building my own costmap inside
> our navigator's address space, but costmap_2d_node provides a handy
> platform for trying out the package.
>
> It looks like this package does what I need quite well, but the
> learning curve has been quite steep so far. There are no Tutorials
> specific to that package; I found some helpful Tutorials for the
> navigation stack, but they are clearly aimed at PR2 navigation tasks.
> The wiki page has lots of useful data, but I had trouble piecing
> together the big picture. I had to consult the source code to figure
> out exactly what <name> and <source_name> actually signify when using
> the costmap_2d_node.
>
> If there are other docs about using the costmap, I could use some pointers.
>
> I did manage to get it publishing some kind of occupancy data for a
> simulated laser in stage. And, I am able to use rviz to view the
> GridCell display, which shows most of the cells as "unknown".
>
> I vaguely recall a discussion about this a while back. For indoor
> robots a max range laser reading is often treated as unknown, because
> there should be walls to reflect any unblocked scans. But outdoors,
> max range scans are the normal case, and need to clear out cells along
> the relevant ray traces.
>
> How do I get the costmap to do that?
> --
>  joq
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