---
pageClass: is-wide-page
---

# ObstacleDistance (UORB message)

Obstacle distances in front of the sensor.

**TOPICS:** obstacle_distance obstacle_distance_fused

## Fields

| Name         | Type         | Unit [Frame] | Range/Enum | Description                                                                                                                                                                                                                                                                                                 |
| ------------ | ------------ | ------------ | ---------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| timestamp    | `uint64`     |              |            | time since system start (microseconds)                                                                                                                                                                                                                                                                      |
| frame        | `uint8`      |              |            | Coordinate frame of reference for the yaw rotation and offset of the sensor data. Defaults to MAV_FRAME_GLOBAL, which is North aligned. For body-mounted sensors use MAV_FRAME_BODY_FRD, which is vehicle front aligned.                                                                                    |
| sensor_type  | `uint8`      |              |            | Type from MAV_DISTANCE_SENSOR enum.                                                                                                                                                                                                                                                                         |
| distances    | `uint16[72]` |              |            | Distance of obstacles around the UAV with index 0 corresponding to local North. A value of 0 means that the obstacle is right in front of the sensor. A value of max_distance +1 means no obstacle is present. A value of UINT16_MAX for unknown/not used. In a array element, one unit corresponds to 1cm. |
| increment    | `float32`    |              |            | Angular width in degrees of each array element.                                                                                                                                                                                                                                                             |
| min_distance | `uint16`     |              |            | Minimum distance the sensor can measure in centimeters.                                                                                                                                                                                                                                                     |
| max_distance | `uint16`     |              |            | Maximum distance the sensor can measure in centimeters.                                                                                                                                                                                                                                                     |
| angle_offset | `float32`    |              |            | Relative angle offset of the 0-index element in the distances array. Value of 0 corresponds to forward. Positive is clockwise direction, negative is counter-clockwise.                                                                                                                                     |

## Constants

| Name                                                                        | Type    | Value | Description |
| --------------------------------------------------------------------------- | ------- | ----- | ----------- |
| <a id="#MAV_FRAME_GLOBAL"></a> MAV_FRAME_GLOBAL                             | `uint8` | 0     |
| <a id="#MAV_FRAME_LOCAL_NED"></a> MAV_FRAME_LOCAL_NED                       | `uint8` | 1     |
| <a id="#MAV_FRAME_BODY_FRD"></a> MAV_FRAME_BODY_FRD                         | `uint8` | 12    |
| <a id="#MAV_DISTANCE_SENSOR_LASER"></a> MAV_DISTANCE_SENSOR_LASER           | `uint8` | 0     |
| <a id="#MAV_DISTANCE_SENSOR_ULTRASOUND"></a> MAV_DISTANCE_SENSOR_ULTRASOUND | `uint8` | 1     |
| <a id="#MAV_DISTANCE_SENSOR_INFRARED"></a> MAV_DISTANCE_SENSOR_INFRARED     | `uint8` | 2     |
| <a id="#MAV_DISTANCE_SENSOR_RADAR"></a> MAV_DISTANCE_SENSOR_RADAR           | `uint8` | 3     |

## Source Message

[Source file (GitHub)](https://github.com/PX4/PX4-Autopilot/blob/main/msg/ObstacleDistance.msg)

::: details Click here to see original file

```c
# Obstacle distances in front of the sensor.
uint64 timestamp		# time since system start (microseconds)

uint8 frame		#Coordinate frame of reference for the yaw rotation and offset of the sensor data. Defaults to MAV_FRAME_GLOBAL, which is North aligned. For body-mounted sensors use MAV_FRAME_BODY_FRD, which is vehicle front aligned.
uint8 MAV_FRAME_GLOBAL = 0
uint8 MAV_FRAME_LOCAL_NED = 1
uint8 MAV_FRAME_BODY_FRD = 12

uint8 sensor_type # Type from MAV_DISTANCE_SENSOR enum.
uint8 MAV_DISTANCE_SENSOR_LASER = 0
uint8 MAV_DISTANCE_SENSOR_ULTRASOUND = 1
uint8 MAV_DISTANCE_SENSOR_INFRARED = 2
uint8 MAV_DISTANCE_SENSOR_RADAR = 3

uint16[72] distances # Distance of obstacles around the UAV with index 0 corresponding to local North. A value of 0 means that the obstacle is right in front of the sensor. A value of max_distance +1 means no obstacle is present. A value of UINT16_MAX for unknown/not used. In a array element, one unit corresponds to 1cm.

float32 increment # Angular width in degrees of each array element.

uint16 min_distance # Minimum distance the sensor can measure in centimeters.
uint16 max_distance # Maximum distance the sensor can measure in centimeters.

float32 angle_offset # Relative angle offset of the 0-index element in the distances array. Value of 0 corresponds to forward. Positive is clockwise direction, negative is counter-clockwise.

# TOPICS obstacle_distance obstacle_distance_fused
```

:::