Meaning of world frame / coordinates in the context of costmaps

asked 2016-04-27 10:06:00 -0600

spmaniato gravatar image

updated 2016-04-27 10:07:38 -0600

I've read a couple of Q&As here regarding the meaning of world frame, as well as REP 105, "Coordinate Frames for Mobile Platforms". I'm still in need of a clarification, especially in the context of costmaps. Let's use an example:

The WorldModel and CostmapModel classes have a member function called footprintCost (see, e.g., the declaration in base_local_planner/costmap_model.h) The documentation says:

@param  position The position of the robot in world coordinates

What is the world frame in this case? Is it the costmap's global_frame, e.g., odom if it's a local costmap? If so, why is there a distinction between world and global?

It seems to me like the world frame is defined relative to some specific context (e.g. a costmap, or a pose estimation scheme). It's not an actually fixed frame in "the world". Is this a good way to think about it? Thanks!

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