Jack,
Here's how I use the messages... though its not an official standard and I expect others may do things differently.
OccupancyGrid: Used for sending maps over ROS. I only use this message for sending occupancy grids from SLAM systems or something like the map_server.
GridCells: Meant for visualization, though some people have started using them for other things. I use them when I want rviz or another visualization tool to be able to display information about certain cells in a 2D grid.
PointCloud: I use this type for publishing sensor data or filtered sensor data.... though this message is used throughout the ROS ecosystem for a variety of different reasons. In the navigation stack at least, a PointCloud typically refers to some observation about obstacles in the world made by a sensor.
Hope this helps,
Eitan
On Tue, Sep 21, 2010 at 2:51 PM, Jack O'Quin
<jack.oquin@gmail.com> wrote:
>> Has there been any consideration of accepting nav_msgs/OccupancyGrid
>> or nav_msgs/GridCells as input?
>
> We're actually working on a node to turn OccupancyGrid messages into
> PointClouds, which are then fed into the costmap. Once we get it finished,
> tested and some usage documentation done, we'll be sharing it.
Thanks.
I don't have any immediate need for it. Mainly, I am trying to
understand the larger picture of how the occupancy grid fits into the
whole system. A large O-grid is hard to share over TCP connections
(except infrequently). PointClouds tend to get big, too. Nodelets seem
to offer higher bandwidth in certain useful cases, but not all.
I am still somewhat confused about how these various messages are
intended to be used in combination. When would we publish an
OccupancyGrid versus GridCells or PointCloud?
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