Polaris is open-source inertial nagivation software (INS) for fixed-wing aircraft. It provides realtime estimates to allow for higher-level navigation software to be developed.

Polaris is a software INS that runs against X-Plane out of the box but can also be used on real hardware.

Polaris is designed to take the following inputs:

• 3-axis accelerometer
• 3-axis gyro
• 3-axis magnetometer (including magnetic declination lookup table)
• Static air sensor (altitude)
• Differential air sensor (indicated airspeed)
• GPS
• Various temperatures (both on the sensors and ambient)

And turn those inputs into a realtime probabilistic model with the following estimates:

• Orientation (pitch, roll, and yaw)
• Position (longitude, latitude, and altitude)
• Speeds (indicated airspeed, true airspeed, speed over ground)
• Wind (x/y/z axis windspeed estimates which help make a more accurate dead-reckoning estimate)

Polaris is able to build and maintain its realtime probabilistic model primarily using an (extended Kalman filter](http://en.wikipedia.org/wiki/Extended_Kalman_filter) (EKF). There are two major steps to the EKF: predicting your current state and updating your model based on what actually happened.

Right now Polaris uses Euler angles but in the future it may use quaternions.

More to come in this section…

1. Local magnetic declination lookup table
2. Get course over ground working (emulated or hpath)
3. Get cpress working (true airspeed / indicated airspeed ratio)
4. Code up alternate algorithms such as DCM and benchmark it against the EKF
5. Quaternion-based EKF
6. More advanced display/logging
7. Clean up website, installation instructions
8. Make a screencast for setting it up and explaining it
9. Port to other platforms
10. Email Austin Meyer (X-Plane) and see if he's willing to include raw magnetometer values
11. Once all the algorithms are verified (including a write-up on the testing perhaps), introduce sensor noise

Have a bug or feature request? Please create an issue here on GitHub!

https://github.com/timtrueman/polaris/issues

Ryan Beall

Tim Trueman

Copyright 2011 Tim Trueman and Ryan Beall

Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0