# Ultrasonics data pre-processing design

## Overview

An ultrasonic sensor measures the distance to the nearest object in a small cone in front of the sensor.

> [!NOTE]
>
> **No ultrasonic processing in Autoware today**
>
> Autoware 2.0.0 has no package that reads, filters, or uses ultrasonic sensor data. No sensor kit in `autoware_launch` launches an ultrasonic driver, and no perception or planning module reads ultrasonic topics.

## Message type

The [input types](<../../#input-types>) table of the sensing component defines the message type for ultrasonic sensors: [`sensor_msgs/msg/Range`](<https://github.com/ros2/common_interfaces/blob/rolling/sensor_msgs/msg/Range.msg>).

A `Range` message holds one distance measurement:

| Field | Type | Description |
| :--- | :--- | :--- |
| `header` | `Header` | The time of the measurement and the frame of the sensor |
| `radiation_type` | `uint8` | `ULTRASOUND` (0) or `INFRARED` (1) |
| `field_of_view` | `float32` | The size of the arc that the measured distance is valid for \[rad\] |
| `min_range` | `float32` | The minimum distance that the sensor can measure \[m\] |
| `max_range` | `float32` | The maximum distance that the sensor can measure \[m\] |
| `range` | `float32` | The measured distance \[m\] |
| `variance` | `float32` | The variance of the measured distance. `0` means unknown. Only in ROS 2 Jazzy and later. |

## Integrate an ultrasonic sensor

To use ultrasonic sensors with Autoware today, you must write the driver and the processing yourself. For example, a driver can publish one `Range` topic for each sensor in the `/sensing` namespace of your sensor kit. Then your own module must convert the measurements into a form that other components read, for example a point cloud or an occupancy grid.