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# Ekf2Timestamps (UORB message)

this message contains the (relative) timestamps of the sensor inputs used by EKF2. It can be used for reproducible replay.

**TOPICS:** ekf2_timestamps

## Fields

| Name                               | Type     | Unit [Frame] | Range/Enum | Description                            |
| ---------------------------------- | -------- | ------------ | ---------- | -------------------------------------- |
| timestamp                          | `uint64` |              |            | time since system start (microseconds) |
| airspeed_timestamp_rel             | `int16`  |              |            |
| airspeed_validated_timestamp_rel   | `int16`  |              |            |
| distance_sensor_timestamp_rel      | `int16`  |              |            |
| optical_flow_timestamp_rel         | `int16`  |              |            |
| vehicle_air_data_timestamp_rel     | `int16`  |              |            |
| vehicle_magnetometer_timestamp_rel | `int16`  |              |            |
| visual_odometry_timestamp_rel      | `int16`  |              |            |

## Constants

| Name                                                                | Type    | Value | Description                                |
| ------------------------------------------------------------------- | ------- | ----- | ------------------------------------------ |
| <a id="#RELATIVE_TIMESTAMP_INVALID"></a> RELATIVE_TIMESTAMP_INVALID | `int16` | 32767 | (0x7fff) If one of the relative timestamps |

## Source Message

[Source file (GitHub)](https://github.com/PX4/PX4-Autopilot/blob/main/msg/Ekf2Timestamps.msg)

::: details Click here to see original file

```c
# this message contains the (relative) timestamps of the sensor inputs used by EKF2.
# It can be used for reproducible replay.

# the timestamp field is the ekf2 reference time and matches the timestamp of
# the sensor_combined topic.

uint64 timestamp			 # time since system start (microseconds)

int16 RELATIVE_TIMESTAMP_INVALID = 32767 # (0x7fff) If one of the relative timestamps
                                         # is set to this value, it means the associated sensor values did not update

# timestamps are relative to the main timestamp and are in 0.1 ms (timestamp +
# *_timestamp_rel = absolute timestamp). For int16, this allows a maximum
# difference of +-3.2s to the sensor_combined topic.

int16 airspeed_timestamp_rel
int16 airspeed_validated_timestamp_rel
int16 distance_sensor_timestamp_rel
int16 optical_flow_timestamp_rel
int16 vehicle_air_data_timestamp_rel
int16 vehicle_magnetometer_timestamp_rel
int16 visual_odometry_timestamp_rel

# Note: this is a high-rate logged topic, so it needs to be as small as possible
```

:::
