# gmapping resolution

I have a basic question.

Rviz shows a resolution of the map of 0.05.

If I have a (x,y) coordinate of [29, 1983], what is the value in meters of the previous coordinate. I mean [x meters, y meters]

My best guess is that every cell has a value of 0.05, but im not sure

Originally posted by acp on ROS Answers with karma: 556 on 2013-06-27

Post score: 0

I think those coordinates are meters yet.

Originally posted by Lucile with karma: 318 on 2013-06-27

This answer was ACCEPTED on the original site

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Comment by acp on 2013-06-27:
well, it think, it can not be, because I have measured the place and has max of 40-45 meters, and 1983*0.05 ans = 99.150

Comment by Lucile on 2013-06-27:
What coordinates are you talking about exactly ?

Comment by acp on 2013-06-27:
But, I may think that every 50 cells is a meter

Comment by Lucile on 2013-06-27:
How could that be ? What coordinates are you talking about exactly ? Where did you find them ?

Comment by acp on 2013-06-27:
The coordinates I have mentioned are the coordinates of the empty area of the global map, they have been taken from the /map topic under gmapping packege. The other issue here is how to relate the initial position of the robot with the origin of the local map.

Comment by acp on 2013-06-27:
I have seen the documentation, and they are 20 cells per meter so it gives a resolution of 0.05. I may have something wrong in the way I get the coordinates from the /map topic under gmapping packege

Comment by Lucile on 2013-06-27:
Well, if you look at here : ros.org/doc/api/nav_msgs/html/msg/MapMetaData.html they say that data from /map topics are given in meters and radians. And they also say in REP 105 that mobile platform's position is relative to the map's frame

Comment by acp on 2013-06-27:
Thnax for the answer, my issue is how to interpret it. I have measured the width of the map, 40-45 m, and I get map.info.width=1984, this means that 1984*0.05= 99.250m, something might be wrong.

Comment by acp on 2013-06-27:
The map.data[i] gives you an array starting from [0,0], and when you make the map based on gmapping, the [0,0] position is where the robot starts. How to make these two origins to coincide.

Comment by Lucile on 2013-06-27:
If you use turtlebot, there are some files in the turtlebot_navigation/param repository... You might give them a look and edit them. And you can also edit the .yaml which is joined to the map that you use. If not, you might have the equivalent files somewhere.

Comment by sudhanshu_mittal on 2013-09-26:
can you once check your following parameter values in the gmapping package launch file ?