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Orientation calibration

Sometimes it's difficult to get the Ruby controller and airspeed/magnetometer both mounted perfecly squarely with the airframe's flight axes.

With this short procedure, you can give Ruby information it needs to accommodate arbitrary mounting angles.


You will need to perform the following procedure outdoors away from any possible sources of magnetic distortion. For instance, you should be more than 20 feet from any automobile.

During the procedure, you'll need to be able to point exactly due magnetic west.  

This can be done using a good magnetic compass, but probably best done if you can find a landmark visible from your outdoor location  that is exactly due magnetic west of where you will be standing with the plane.

To find an appropriate landmark without a compass, use http://magnetic-declination.com/ to determine magnetic declination at your location. For instance, in Boston, the magnetic declination is -15 degrees "West", so magnetic west is 270 - 15 = 265 degrees true.

Note that the compasses built into many smart phones / tablets tend to be inaccurate.

Then use a map or Google Earth to look at an outdoor location near you with some kind of landmark with that heading from your outdoor location. It could be a radio tower in the distance or a tree a hundred feet away. Use the "ruler" tool in Google Earth to measure true compass heading between your test location and the landmark.


click to enlarge

Ideally, but not necessarily, you'll also have a spirit level (with no steel / ferrous parts) so that you can be sure the plane is perfectly level.


Power up the plane and transmitter.

Flip switch 7 times from and to autonomous position while holding aileron / elevator stick in any corner, then release the stick.

The elevator should wag 2 times to acknowledge that it is in "orientation calibration" mode.

If no gps lock has been acquired or the magnetometer is distorted or not properly calibrated, the ailerons will wag. If you're not able to get the elevator to wag even after waiting 2 minutes for GPS to acquire satellites, check that the magnetometer is not distorted or miscalibrated. [more info...]. If still no resolution, send the data.utd file recorded during your attempt to support@uthere.com.


Hold plane by nose and point tail to exactly due magnetic west while keeping plane completely level (use spirit level if needed).

Remember to point the plane's *tail* and not the nose to magnetic west.

Move elevator / aileron stick to corner. (You'll probably have to use an assistant or set transmitter on ground and use your foot.)

Elevator will wag once


Roll plane so that right wing is pointing straight up, the fuselage completely level, and tail still pointed to west.

Remember - you're lifting the plane's right wing (which is at your left hand), not your right hand.

Move elevator / aileron stick to corner. Elevator will wag 7 times to indicate success..


It's OK if the fulelage isn't kept level as you roll the plane, but it must be level at the moment you flip the stick.

For best precision, balancing a wing on the ground and using a spirit level or friend looking at the plane from the side can be helpful.

That's it - Ruby will store the orientation in internal memory.  This will remain in effect until the next time you update configuration or firmware.

WARNING: If you've made a mistake in the above procedure, it's possible to totally disorient Ruby in a way that will lead to a crash. Perform a "test before first flight" and follow the "cautious first flight" guidelines, engaging Ruby for first time at safe altitude,etc...

To better confirm that the procedure has been performed accurately, make the plane completely level and point the nose at one or more precisely known directions. Use Ground Control to review true heading, pitch, and roll (View: User Type: Expert, then View: Instrument Bar) in telemetry or the recorded data.utd file and see if they match the actual plane. Remember that all directions are given in degrees true, not magnetic. Heading, yaw, and roll should all be accurate to within 5 degrees. If not, repeat the above procedure, being careful to precisely point the plane and be sure that the fuselage centerline is completely level at each step. If inaccuracy persists, see: [magnetometer troubleshoot].



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