> For the complete documentation index, see [llms.txt](https://px4.gitbook.io/px4-user-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://px4.gitbook.io/px4-user-guide/development/modules_main/modules_estimator.md).

# Estimators

## AttitudeEstimatorQ

Source: [modules/attitude\_estimator\_q](https://github.com/PX4/PX4-Autopilot/tree/main/src/modules/attitude_estimator_q)

### Description

Attitude estimator q.

### Usage

```
AttitudeEstimatorQ <command> [arguments...]
 Commands:
   start

   stop

   status        print status info
```

## airspeed\_estimator

Source: [modules/airspeed\_selector](https://github.com/PX4/PX4-Autopilot/tree/main/src/modules/airspeed_selector)

### Description

This module provides a single airspeed\_validated topic, containing indicated (IAS), calibrated (CAS), true airspeed (TAS) and the information if the estimation currently is invalid and if based sensor readings or on groundspeed minus windspeed. Supporting the input of multiple "raw" airspeed inputs, this module automatically switches to a valid sensor in case of failure detection. For failure detection as well as for the estimation of a scale factor from IAS to CAS, it runs several wind estimators and also publishes those.

### Usage

```
airspeed_estimator <command> [arguments...]
 Commands:
   start

   stop

   status        print status info
```

## ekf2

Source: [modules/ekf2](https://github.com/PX4/PX4-Autopilot/tree/main/src/modules/ekf2)

### Description

Attitude and position estimator using an Extended Kalman Filter. It is used for Multirotors and Fixed-Wing.

The documentation can be found on the [ECL/EKF Overview & Tuning](https://docs.px4.io/main/en/advanced_config/tuning_the_ecl_ekf.html) page.

ekf2 can be started in replay mode (`-r`): in this mode, it does not access the system time, but only uses the timestamps from the sensor topics.

### Usage

```
ekf2 <command> [arguments...]
 Commands:
   start
     [-r]        Enable replay mode

   stop

   status        print status info

   select_instance Request switch to new estimator instance
     <instance>  Specify desired estimator instance
```

## local\_position\_estimator

Source: [modules/local\_position\_estimator](https://github.com/PX4/PX4-Autopilot/tree/main/src/modules/local_position_estimator)

### Description

Attitude and position estimator using an Extended Kalman Filter.

### Usage

```
local_position_estimator <command> [arguments...]
 Commands:
   start

   stop

   status        print status info
```

## mc\_hover\_thrust\_estimator

Source: [modules/mc\_hover\_thrust\_estimator](https://github.com/PX4/PX4-Autopilot/tree/main/src/modules/mc_hover_thrust_estimator)

### Description

### Usage

```
mc_hover_thrust_estimator <command> [arguments...]
 Commands:
   start

   stop

   status        print status info
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://px4.gitbook.io/px4-user-guide/development/modules_main/modules_estimator.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.