[ros-users] navigation stack bare minimums

[Mike Purvis]

>
> Mike, while the tutorial for setting up the navigation stack says that you
> can just set the static_map: yaml setting to false if you don't have a map
> server, I have found it easier to just setup a map server and give it a
> small white image, basically just a blank map.
>

Okay, cool. I added a small note to the global_costmap section of the
wikipage clarifying this.

For the moment, I'll try just using false; if that doesn't work out, I'll
experiment with a blank map.

You can also set all costmaps to rolling windows with their global
> frame as /odom. As long as you actually publish a tf between that and
> base_link (or whatever you want to call your equivalent frames), you
> should be able to run completely without a map server. I can
> definitely say that it is possible to run navigation without a static
> map - I am currently doing just that and have had no issues related to
> lack of map server.
>

Okay, cool. For the moment, my preference would be to avoid map_server. Our
initial ROS deployment is for a lightweight open-water craft, so it's
unnecessary.


> As far as required transforms goes, you really ought to be publishing
> transforms for the different frames. You could use the
> static_transform_publisher node to publish a static transform, but the
> transform from base_link to odom is not static, so you will need to
> broadcast that transform yourself.Another option is to use one of the
> existing simulators (stage and gazebo) that hook into ROS, which
> broadcast all the transforms you should need.


The documentation I've been following for this process is at
navigation/Tutorials/RobotSetup/TF, which just speaks about setting up a
transform between base_link and a sub-part (laser scanner). Is there
somewhere else I need to be looking for information about the base_link ->
odom and base_link -> map transforms? What do these transforms represent,
and what's the relationship between them and the information that's already
in my odom topic?

If I make the base_link not be on-board the robot, are there ways that it's
going to bite me later if/when I do end up adding a map, or if I'm trying to
set up a multi-robot system?

Sorry for the barrage of questions, but I really appreciate your assistance.
I'm trying to do my best document things as I discover them, to help out
future newbies.

Mike
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