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Gazebo Ray / LIDAR / Ultrasonic sensor

Simulation / Gazebo / sensors

ray sensor

For the current state gazebo not support ray and ultrasonic sensor when we declare ray sensor we got the following error 

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[Wrn] [SdfEntityCreator.cc:1097] Sensor type LIDAR not supported yet. Try using a GPU LIDAR instead.

use <sensor name="ultrasonic" type="gpu_ray"> and not <sensor name="ultrasonic" type="ray">

plugin
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<plugin
    filename="gz-sim-sensors-system"
    name="gz::sim::systems::Sensors">
    <render_engine>ogre2</render_engine>
</plugin>

Sensor definition

Sdf specification

gpu_ray sensor
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<sensor name="ultrasonic_lidar" type="gpu_lidar">
    <pose>0 0 0 0 0 0</pose>
    <always_on>1</always_on>
    <update_rate>20</update_rate>
    <visualize>true</visualize>
    <topic>ultrasonic_lidar</topic>

    <ray>
        <scan>
            <horizontal>
                <samples>5</samples>
                <resolution>1</resolution>
                <min_angle>-0.26</min_angle>
                <max_angle>0.26</max_angle>
            </horizontal>
            <vertical>
                <samples>3</samples>
                <resolution>1</resolution>
                <min_angle>-0.10</min_angle>
                <max_angle>0.10</max_angle>
            </vertical>
        </scan>

        <range>
            <min>0.02</min>
            <max>10.0</max>
            <resolution>0.01</resolution>
        </range>
    </ray>
</sensor>

Add noise

sensor with noise
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<sensor name="ultrasonic" type="gpu_ray">
  <pose>0.5 0 0.5 0 0 0</pose>
  <always_on>true</always_on>
  <update_rate>10</update_rate>
  <visualize>true</visualize>
  <topic>ultrasonic_range</topic>

  <ray>
      <scan>
          <horizontal>
              <samples>1</samples>
              <resolution>1</resolution>
              <min_angle>0.0</min_angle>
              <max_angle>0.0</max_angle>
          </horizontal>
      </scan>
      <range>
          <min>0.02</min>      <!-- 2 cm -->
          <max>4.0</max>       <!-- 4 meters -->
          <resolution>0.001</resolution>

      </range>
      <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.30</stddev>  <!-- 30cm noise -->
      </noise>
  </ray>
</sensor>

Noise explain

alt text

  • The mean (red dashed line at 0.0) is the average noise, meaning most measurements will center around the true value.

  • The standard deviation (σ = 0.30 m) controls the spread:

  • ~68% of readings fall between −0.30 m and +0.30 m (green dashed lines).
  • Occasionally, the noise will be larger, simulating sensor error or measurement variation.

message

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header {
  stamp {
    sec: 20
    nsec: 200000000
  }
  data {
    key: "frame_id"
    value: "my_box::box_link::ultrasonic"
  }
  data {
    key: "seq"
    value: "202"
  }
}
frame: "my_box::box_link::ultrasonic"
world_pose {
  position {
    x: 0.5
    z: 0.5
  }
  orientation {
    w: 1
  }
}
angle_step: nan
range_min: 0.02
range_max: 4
count: 1
vertical_angle_step: nan
vertical_count: 1
ranges: 1.0000607967376709
intensities: 0

world_pose

The sensor position and orientation inside the container link

Range

ranges field contain reading for each ray in our case just one reading

Demo

world with ray sensor 
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<?xml version="1.0"?>
<sdf version="1.10">
    <world name="ultrasonic_lidar_world">

        <physics name="1ms" type="ignored">
            <max_step_size>0.001</max_step_size>
            <real_time_factor>1.0</real_time_factor>
        </physics>

        <plugin
            filename="gz-sim-physics-system"
            name="gz::sim::systems::Physics" />
        <plugin
            filename="gz-sim-sensors-system"
            name="gz::sim::systems::Sensors">
            <render_engine>ogre2</render_engine>
        </plugin>
        <plugin
            filename="gz-sim-scene-broadcaster-system"
            name="gz::sim::systems::SceneBroadcaster" />

        <light name="sun" type="directional">
            <pose>0 0 10 0 0 0</pose>
            <diffuse>0.8 0.8 0.8 1</diffuse>
            <specular>0.2 0.2 0.2 1</specular>
            <direction>-0.5 0.1 -0.9</direction>
        </light>

        <model name="sensor_model">
            <static>true</static>
            <pose>0 0 0 0 0 0</pose>

            <link name="sensor_link">
                <pose>0 0 0.2 0 0 0</pose>

                <visual name="sensor_visual">
                    <geometry>
                        <box>
                            <size>0.2 0.1 0.1</size>
                        </box>
                    </geometry>
                    <material>
                        <diffuse>0 0 1 1</diffuse>
                    </material>
                </visual>

                <collision name="sensor_collision">
                    <geometry>
                        <box>
                            <size>0.2 0.1 0.1</size>
                        </box>
                    </geometry>
                </collision>

                <!-- Ultrasonic-like sensor using CPU lidar rays -->
                <sensor name="ultrasonic_lidar" type="gpu_lidar">
                    <pose>0 0 0 0 0 0</pose>
                    <always_on>1</always_on>
                    <update_rate>20</update_rate>
                    <visualize>true</visualize>
                    <topic>ultrasonic_lidar</topic>

                    <ray>
                        <scan>
                            <horizontal>
                                <samples>5</samples>
                                <resolution>1</resolution>
                                <min_angle>-0.26</min_angle>
                                <max_angle>0.26</max_angle>
                            </horizontal>
                            <vertical>
                                <samples>3</samples>
                                <resolution>1</resolution>
                                <min_angle>-0.10</min_angle>
                                <max_angle>0.10</max_angle>
                            </vertical>
                        </scan>

                        <range>
                            <min>0.02</min>
                            <max>10.0</max>
                            <resolution>0.01</resolution>
                        </range>
                    </ray>
                </sensor>
            </link>
        </model>

        <!-- Box 5 meters in front of the sensor along +X -->
        <model name="target_box">
            <static>true</static>
            <pose>5 0 0.5 0 0 0</pose>

            <link name="box_link">
                <collision name="collision">
                    <geometry>
                        <box>
                            <size>1 1 1</size>
                        </box>
                    </geometry>
                </collision>

                <visual name="visual">
                    <geometry>
                        <box>
                            <size>1 1 1</size>
                        </box>
                    </geometry>
                    <material>
                        <diffuse>1 0 0 1</diffuse>
                    </material>
                </visual>
            </link>
        </model>

    </world>
</sdf>

alt text

Show the same data as ray and filter only ray that hit the target alt text

Python binding

download code

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import math
import time

from gz.transport13 import Node
from gz.msgs10.laserscan_pb2 import LaserScan

TOPIC = "/ultrasonic_lidar"


def lidar_cb(msg: LaserScan):
    valid_ranges = [
        r for r in msg.ranges
        if math.isfinite(r) and msg.range_min <= r <= msg.range_max
    ]

    if not valid_ranges:
        print("No object detected")
        return

    distance = min(valid_ranges)
    print(f"Distance to object: {distance:.3f} m")


def main():
    node = Node()

    ok = node.subscribe(LaserScan, TOPIC, lidar_cb)
    if not ok:
        raise RuntimeError(f"Failed to subscribe to {TOPIC}")

    print(f"Listening on {TOPIC}...")

    try:
        while True:
            time.sleep(0.1)
    except KeyboardInterrupt:
        print("Stopping")


if __name__ == "__main__":
    main()