extracting values from laser scan data!

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@Ravi Joshi thanks, i received the point cloud from 3d lidar. and i used pointcloud_to_laserscan package. as i checked depthimage_to_laserscan, it is for melodic and noetic. i am working with kinetic 16.04.

I have converted pointcloud from 3d lidar, to laserscan. i just wanted to extract the first three minimum values (as i have three objects infront of my robot).

How about sorting the received scan, say ranges attribute in sensor_msgs/LaserScan.msg, and then take the first 3 values? Of course, this assumes that there is only one point on every object, which is not a correct approach. But please check your LaserScan.msg by plotting it. You may apply clustering to get 3 clusters (instead of 3 points). BTW, do not forget to set ~range_min and ~range_max in pointcloud_to_laserscan_node.

@Ravi Joshi , sorry, is there any way to first remove/or filter the environment noise from the point cloud, and then convert the point cloud to the laser scan data? becasue when i convert the pointcloud into laser scan, it provides me the ranges of the points that are too far from the robot and relate to the environment, if i could remove them it was good.

I am having difficulty understanding the problem correctly. When you say "that are too far from the robot", I wonder why don't you set ~range_max param in the first place.

Dear @Ravi Joshi I know what you are mening. i have set the range_max = 10 , but as you can see in the attached image, in the right side top, those points are showing to me. i donot want them. i want the points in the middle.

@Ravi Joshi Thanks a lot for your support. The issue solved.