Meaning of each parameters in sensor_msgs/LaserScan

[Kening Ren]

Hi,

I am trying to use XV11 LiDAR device with cartographer_ros to generate the 2D map.  I am using message sensor_msgs/LaserScan to send data to cartographer_ros.

As you may know, each data packet sent from XV11 LiDAR carries 4 data. Each data has the distance and the angle. And my code receives one data packet and then sends one LaserScan message  

However I do not know how to set some parameters of LaserScan message:

1, time_increment.  It is said to be the time between measurements. In my case, What is it exactly? Is it the time between capturing each distance-angle?

2, scan_time. It is said to be the time between scans. In my case, what is it exactly? 

3, range_min and range_max. XV11 LiDAR sends out 4 range-angle pairs at a time. Can I set range_min to be the min of the 4 ranges and range_max to the the max of the 4 ranges?

4, angle_min and angle_max. Can I set angle_min to be the min of the 4 angles and max to the max of the 4 angles?

5, angle_increment. It is said to be angular distance between measurements. Can I set it as the difference between angle_max and angle_min?

Thank you.

--Kening

For your reference, below is the format of the message.

Header header            # timestamp in the header is the acquisition time of 
                         # the first ray in the scan.
                         #
                         # in frame frame_id, angles are measured around 
                         # the positive Z axis (counterclockwise, if Z is up)
                         # with zero angle being forward along the x axis
                         
float32 angle_min        # start angle of the scan [rad]
float32 angle_max        # end angle of the scan [rad]
float32 angle_increment  # angular distance between measurements [rad]

float32 time_increment   # time between measurements [seconds] - if your scanner
                         # is moving, this will be used in interpolating position
                         # of 3d points
float32 scan_time        # time between scans [seconds]

float32 range_min        # minimum range value [m]
float32 range_max        # maximum range value [m]

float32[] ranges         # range data [m] (Note: values < range_min or > range_max should be discarded)
float32[] intensities    # intensity data [device-specific units].  If your
                         # device does not provide intensities, please leave
                         # the array empty.

[Damon Kohler]

Hi Kening,

This is best addressed on the ROS forums as it is not a Cartographer-specific question. Try posting on http://answers.ros.org/

Damon

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