InertialNav

InertialNav App is primarily an attitude indicator, with the following instruments:
- artificial horizon.
- altimeter
- compass (magnetic)
- speed meter (groundspeed, vertical Speed)
- ground track

A HUD mode allows using the application for augmented reality. You can also displau a Google Map and your position.
Real-time measurements and estimations can be exported to a text file for post-processing (e.g. into MATLAB, SciLab or Octave).


HOW DOES IT WORK?
In real life environment, sensors tend to measure noises in addition to the physical quantity of interest. The current application provides an estimate of the attitude. To have the best estimation of the attitude an Extended Kalman Filter (EKF) is implemented. The filter purpose is to reject all perturbations, but to do so efficiently, it needs different sources of measurments. Considering we are interested by the orientation, and your device is indeed an inertial measurement unit (IMU with gyroscopes, accelerometers and so on), using gyroscopes for angular velocity and a set of measurements from accelerometers and magnetometers, we can indeed estimate the attitude with our EKF.
That is, to estimate the attitude, the EKF will sometimes discard information from the sensors that it deems unreliable or too noisy - it may sometimes favour the attitude measurements rather than the angular velocity integration and vice versa - to minimise the covariance of the error. Furthermore, quaternion formulation for the orientation makes the estimation very robust.
Additionally, if GPS is available, sub-meter positioning can be obtained. That is, this can not work efficiently indoors (drift in position and velocity).

** IMPORTANT ** : depending on your device, please consider going through the covariance settings for best estimation of the attitude! The KF may disregard the measurements if deemed unreliable. If YOU THINK the app does not use the gyroscopes, please CHECK the variance settings for the gyroscopes. The values to enter can be quite large. Try 0.1 and 1e2 for instance, and reverse.

How can you know whether the app uses gyroscopes or accerometers only?
- without gyroscopes, but with accelerometers, the attitude is very noisy (e.g. fast "jumps").
- without the accelerometers, but with the gyroscopes, the attitude is very smooth (because of the integration of gyro data), but there is a slow drift of the attitude increasing with time.



MINIMUM REQUIREMENTS
For best performances, accelerometers, gyroscopes and magnetometers must be present on the device.

Minimum requirements: accelerometers, gyroscopes, magnetometers.
Optional requirements: GPS, camera.
(HeadUp Display will only be available when a camera is available.)

The application is provided as-is, without any warranty. The application is not certified for navigation purposes by any agency or organisation.

If you find bugs, please report by email. Thanks!
Tested on Samsung Galaxy S2.

Recent changes:
Add two new settings to test accelerometers and gyroscopes estimates.
Add dash board for measures and estimates.
Thanks for reporting bugs.

Latest version: 0.3.0 ()