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Change occupancy value in dummy_map_server to 1. #680

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Change occupancy value in dummy_map_server to 1. #680

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2 changes: 1 addition & 1 deletion dummy_robot/dummy_map_server/src/dummy_map_server.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@ int main(int argc, char * argv[])
msg.data[(center) % (msg.info.width * msg.info.height)] = -1;
msg.data[(rhs) % (msg.info.width * msg.info.height)] = -1;
msg.data[(++lhs) % (msg.info.width * msg.info.height)] = 0;
msg.data[(++center) % (msg.info.width * msg.info.height)] = 100;
msg.data[(++center) % (msg.info.width * msg.info.height)] = 1;
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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.

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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.

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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.

msg.data[(++rhs) % (msg.info.width * msg.info.height)] = 0;

msg.header.stamp = clock->now();
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