ROS Resources: Documentation | Support | Discussion Forum | Index | Service Status | ros @ Robotics Stack Exchange
Ask Your Question
0

Relationship between /scan and /map

asked 2020-05-19 10:30:46 -0600

namayna gravatar image

updated 2022-03-20 09:47:49 -0600

lucasw gravatar image

I'm running a hector mapping program that opens rviz and maps as you manually move around the map. I subscribe to both /scan and /map to get the laser scan data and the occupancy grid of the map continuously. I was wondering how exactly the relationship between the scan and the occupancy grid works. Does the occupancy grid update 1:1 with our scan? Or does the scan go past our occupancy grid (or vice versa)?

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted
1

answered 2020-05-19 11:11:42 -0600

bob-ROS gravatar image

This depends on what settings you use. http://wiki.ros.org/hector_mapping

The description of the map: "Get the map data from this topic, which is latched, and updated periodically " And we having settings such as: "laser_max_dist" and "laser_min_dist".

Does the occupancy grid update 1:1 with our scan? Or does the scan go past our occupancy grid (or vice versa)

No, especially when the scan can likely be 50hz and higher, the map will be updated periodically (this does not mean the algorithm can't process all the scans). In fact, the publish rate of the map is based on the parameter "map_pub_period" which will at default publish the map at 0.5Hz. See here.

If you use laser_max_dist and laser_min_dist with a narrow interval the scan will go far beyond the occupancy grid.

edit flag offensive delete link more

Comments

Ah, so in that github code's case, the map will be able to see up to 30 meters away? Also, is there a way to see at what distance map values can be updated (e.g. map can only "see" 20 meters away)?

namayna gravatar image namayna  ( 2020-05-19 13:23:45 -0600 )edit

Question Tools

2 followers

Stats

Asked: 2020-05-19 10:30:46 -0600

Seen: 259 times

Last updated: May 19 '20