[ros-users] Different maps for navigation and path planning

[Christian Verbeek]

>
> You're right. Right now there's not a great way to specify a
> "forbidden zone" in a map. If you specify the space as occupied, then
> sensors can clear it out when it is observed to be free. I've always
> intended on adding a different cost value that designates space as
> forbidden no matter what local sensor information says, but honestly
> just haven't gotten around to it. Since this seems like a critical
> thing for you, and something that a lot of people will want, I've
> created a ticket for it
> here: https://code.ros.org/trac/ros-pkg/ticket/4409.
>
> In the meantime, as you alluded to, you can create a marking sensor
> that asserts that the "forbidden" region is seen as occupied and hook
> it up to the costmap. This will keep the LIDAR from clearing it out
> when the robot is close to it. It isn't quite as easy as drawing on a
> bitmap, but it should solve your problem. You can also have that
> sensor operate at a different height than your LIDAR in the voxel grid
> version of the costmap which means you'll only have to publish
> information about forbidden regions on startup. If you do create the
> sensor that reads in maps to create forbidden zones, it might be nice
> to share it with the ROS community, as the cost value fix likely won't
> be released until D-Turtle.
>
> Come to think of it, the sensor approach is actually much better for
> dealing with the local planner's costmap which has no knowledge of the
> global static map. I'll have to think a little on the best way to deal
> with that with the special cost value approach.
Eitan, Eric,

The solution to my problem was much easier. I simply removed the
rangefinder from the global costmap configuration. So my global map is
really static and the forbidden zones are not cleared out any more. The
working environment of my robot is highly structured so its reasonable
to simply stop the robot when it can not follow the global path and ask
someone to either remove the obstacle or to recreate the map.

But of course this is a simple work around.