Change occupancy value in dummy_map_server to 1.

[marcoag]

As pointed out in osrf/ros2_test_cases#1200, dummy map server occupancy value should be 1 as specified in https://github.com/ros2/common_interfaces/blob/rolling/nav_msgs/msg/OccupancyGrid.msg.

We should backport this once merged.

[clalancette]

I talked to @marcoag about this offline; I have some vague recollection that 100 means something in occupancy grids.

That said, I think that either this number should match what we have in the documentation (which does indeed say to use 1 here), or the documentation should be updated to specifically say that 100 has meaning.

[marcoag]

So in ROS noetic it seems that it was 100 to represent percentage based probabilities. Then this was changed in the last comments update.

There were some efforts to change this to 0-255 for higher resolution here but it was not pursued in order to avoid disruption to users which makes me thing a change to 0-1 would have also been avoided. It seems that now nav2 uses the 0-255 range in costmaps and translates to 0-100 range.

Even though not a percentage anymore I found some uses of the 0-100 range, i.e.: https://github.com/open-navigation/navigation2/blob/main/nav2_costmap_2d/src/costmap_2d_publisher.cpp#L94.

Maybe @DLu can offer some extra info on why a binary value is suggested in the message doc instead of a percentage?

My current naive vote is that we should keep 0-100 and update docs where needed.

[DLu]

So, now in 2024, almost exactly four years after I made ros2/common_interfaces#117, I now question what the heck I was doing. Specifically with the value of 1. Most frequently, its 100.

My full thoughts on the values published in Occupancy Grids can be seen in the robot_navigation documentation. To stay consistent with the RViz visualization, I would probably stick with 100.