# Switching State Estimators

This page shows you which state estimators are available and how you can switch between them.

:::tip EKF2 is highly recommended on vehicles with a GNSS/GPS. The Q-Estimator is recommended if you don't have GPS, and is commonly used in [multicopter racers](https://px4.gitbook.io/px4-user-guide/airframes/frames_multicopter/config_mc/racer_setup). :::

## Available Estimators

The available estimators are:

* **EKF2 attitude, position and wind states estimator** (*recommended*) - An extended Kalman filter estimating attitude, 3D position / velocity and wind states.
* **LPE position estimator** (*deprecated*) - An extended Kalman filter for 3D position and velocity states.

  :::warning LPE is deprecated. It works (at time of writing, in PX4 v1.14) but is no longer supported or maintained. :::
* **Q attitude estimator** - A very simple, quaternion based complementary filter for attitude. It does not require a GPS, magnetometer, or barometer.

## How to Enable Different Estimators

For multirotors and VTOL use the parameter [SYS\_MC\_EST\_GROUP](https://px4.gitbook.io/px4-user-guide/advanced_config/parameter_reference#SYS_MC_EST_GROUP) to choose between the following configurations (LPE is not supported for Fixed Wing).

| SYS\_MC\_EST\_GROUP | Q Estimator | LPE     | EKF2    |
| ------------------- | ----------- | ------- | ------- |
| 1                   | enabled     | enabled |         |
| 2                   |             |         | enabled |
| 3                   | enabled     |         |         |

:::note For FMU-v2 (only) you will also need to build PX4 to specifically include required estimator (e.g. EKF2: `make px4_fmu-v2`, LPE: `make px4_fmu-v2_lpe`). This is required because FMU-v2 is too resource constrained to include both estimators. Other Pixhawk FMU versions include both. :::
