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