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what are the intesity values from gazebo-ros-laser plugin

asked 2018-11-29 07:04:36 -0500

kump gravatar image

The gazebo_ros_laser plugin sends sensor_msgs/LaserScan messages, that contain list of floats called intensities.

sensor_msgs/LaserScan:

std_msgs/Header header
  uint32 seq
  time stamp
  string frame_id
float32 angle_min
float32 angle_max
float32 angle_increment
float32 time_increment
float32 scan_time
float32 range_min
float32 range_max
float32[] ranges
float32[] intensities

Inside the the gazebo_ros_laser plugin source file, the list is being filled with following code.

std::copy(_msg->scan().intensities().begin(),
            _msg->scan().intensities().end(),
laser_msg.intensities.begin());

I understand the ranges list contains the distance to closest obstacle intercepted by the ray, but what does physically the intensity values represent?

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answered 2018-11-29 07:13:36 -0500

sberg gravatar image

Its a measurement of the intensity of the reading, for example reflectors will have a higher value. It can be used to classify the objects that are being scanned. Google e.g."lidar intensity data" for more info.

For many applications it can be safely ignored.

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How does Gazebo compute the intensities?

kump gravatar imagekump ( 2018-11-29 07:37:22 -0500 )edit

Sorry can't help you with that I concluded they were uneeded for my purposes and didn't spend more time on it.

I would look into the wiki (when it comes back online) or the gazebo documentation alternatively LIDAR data sheets

sberg gravatar imagesberg ( 2018-11-29 07:53:49 -0500 )edit

There is no really solid standard of exactly what the intensity values of LiDAR mean. fundamentally it's the intensity of the reflected pulse but some sensors normalise it bases upon range. The best want to think of it is the NIR 'color channel' of the target surface.

PeteBlackerThe3rd gravatar imagePeteBlackerThe3rd ( 2018-11-29 08:22:52 -0500 )edit

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Asked: 2018-11-29 07:04:36 -0500

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Last updated: Nov 29 '18