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# VehicleOpticalFlow (UORB message)

Optical flow in XYZ body frame in SI units.

**TOPICS:** vehicle_optical_flow

## Fields

| Name                    | Type         | Unit [Frame] | Range/Enum | Description                                                                                                                                    |
| ----------------------- | ------------ | ------------ | ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
| timestamp               | `uint64`     |              |            | time since system start (microseconds)                                                                                                         |
| timestamp_sample        | `uint64`     |              |            |
| device_id               | `uint32`     |              |            | unique device ID for the sensor that does not change between power cycles                                                                      |
| pixel_flow              | `float32[2]` |              |            | (radians) accumulated optical flow in radians where a positive value is produced by a RH rotation about the body axis                          |
| delta_angle             | `float32[3]` |              |            | (radians) accumulated gyro radians where a positive value is produced by a RH rotation of the sensor about the body axis. (NAN if unavailable) |
| distance_m              | `float32`    |              |            | (meters) Distance to the center of the flow field (NAN if unavailable)                                                                         |
| integration_timespan_us | `uint32`     |              |            | (microseconds) accumulation timespan in microseconds                                                                                           |
| quality                 | `uint8`      |              |            | Average of quality of accumulated frames, 0: bad quality, 255: maximum quality                                                                 |
| max_flow_rate           | `float32`    |              |            | (radians/s) Magnitude of maximum angular which the optical flow sensor can measure reliably                                                    |
| min_ground_distance     | `float32`    |              |            | (meters) Minimum distance from ground at which the optical flow sensor operates reliably                                                       |
| max_ground_distance     | `float32`    |              |            | (meters) Maximum distance from ground at which the optical flow sensor operates reliably                                                       |

## Source Message

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

::: details Click here to see original file

```c
# Optical flow in XYZ body frame in SI units.

uint64 timestamp               # time since system start (microseconds)
uint64 timestamp_sample

uint32 device_id               # unique device ID for the sensor that does not change between power cycles

float32[2] pixel_flow          # (radians) accumulated optical flow in radians where a positive value is produced by a RH rotation about the body axis

float32[3] delta_angle         # (radians) accumulated gyro radians where a positive value is produced by a RH rotation of the sensor about the body axis. (NAN if unavailable)

float32 distance_m             # (meters) Distance to the center of the flow field (NAN if unavailable)

uint32 integration_timespan_us # (microseconds) accumulation timespan in microseconds

uint8 quality                  # Average of quality of accumulated frames, 0: bad quality, 255: maximum quality

float32 max_flow_rate          # (radians/s) Magnitude of maximum angular which the optical flow sensor can measure reliably

float32 min_ground_distance    # (meters) Minimum distance from ground at which the optical flow sensor operates reliably
float32 max_ground_distance    # (meters) Maximum distance from ground at which the optical flow sensor operates reliably
```

:::