README.md

laserscan_to_ranges

The laserscan_to_ranges package offers simplification and intuitive representation of the LaserScan messages.

Overview

The package subscribes to a LaserScan data and splits it into three equal sectors: left, front, and right. Each sector is describe by only a single floating point value calculation of which can be specified via a parameter. By default, the closest point of the given sector will be used. The package is useful for building simple navigation and obstacle avoidance algorithms.

The resulting data is published as a custom SimpleRanges message containing the following fields:

• left: range of the left sector
• front: range of the front sector
• right: range of the right sector

ROS API

Subscribed topics

• ~/scan (sensor_msgs/LaserScan) - the LaserScan data

Published topics

• ~/simple_ranges (laserscan_to_ranges/SimpleRanges) - the simplified LaserScan data
• Optional topics (enabled via the enable_ranges parameter):
  • ~/ranges_left (sensor_msgs/Range) - the left sector range
  • ~/ranges_front (sensor_msgs/Range) - the front sector range
  • ~/ranges_right (sensor_msgs/Range) - the right sector range

Parameters

The package has the following parameters:

• method (string, default: min) - specifies the method for the range calculation. The following options are available:
  • min: the closest distance in the sector
  • mean: the mean distance in the sector
  • max: the farthest distance in the sector
• field_of_view (double, default: 0.0) - specifies the field of view of the sensor in degrees. If the value is set to 0.0, the field of view will be calculated from the angle_min and angle_max fields of the LaserScan message.
• angle_offset (double, default: 0.0) - specifies the angle offset in degrees. The offset is added to the angle_min and angle_max of the LaserScan messages. For example, if the sensors field of view is [-90, 90] degrees and the offset is 10 degrees, the 60 degree front sector will be shifted from [-30, 30] to [-20, 40].
• enable_ranges (bool, default: false) - By default the node publish only SimpleRanges messages on the simple_ranges topic. Enable this parameter to additionally publish the sensor_msgs/Range messages on the ranges_right, ranges_front, and ranges_left topics. Transforms for each sector are also published. This option is useful for visualization the ranges in RViz.
• debug (bool, default: false) - enable this parameter to start the node with log level set to DEBUG.

Running

To run the node, simply enter:
ros2 run laserscan_to_ranges laserscan_to_ranges

To run the node with parameters, enter:
ros2 run laserscan_to_ranges laserscan_to_ranges --ros-args -p enable_ranges -p method:=mean -p debug:=true

or use the launch file:
ros2 launch laserscan_to_ranges laserscan_to_ranges.launch.py --ros-args -p enable_ranges -p method:=mean -p debug:=true