Orientation Sensor tool

[Scott Ferguson]

This tool displays graphs of the four property values returned by App Inventor's OrientationSensor component:

• Pitch - contains values indicating if the device has been tilted forward or backward relative to horizontal
  
• Roll - contains values indicating if the device has been tilted left or right relative to horizontal
• Angle - contains values indicating how much the device is tilted from vertical, side to side
• Azimuth - contains values indicating a heading relative to *magnetic north

*Note that magnetic north's heading varies by location, date and time and is not the same as true north (which does not vary).

For this reason many digital compass apps provide logic to compensate for that difference (called declination.)

So the raw values returned by the digital compass component of the orientation sensor are relative to magnetic north only.

Here are some sample results from the app which show the values returned by the above properties:

Azimuth - Azimuth values are in the range 0 <= Azimuth < 360 degrees.

(During this test the tablet was kept horizontal, but there are accelerometer sensors built-in to allow you to pick up the tablet and hold it vertically and still get an accurate reading.)

Using the blue scale on the right below...

It was slowly rotated to the East (90 degrees)

Then South (180 degrees)

Then West (270 degrees)

And finally back to North again (0 degrees)

Since 359 degrees and 0 degrees are only one degree apart, there are some vertical lines at the right 

Pitch - ranges from -90 degrees to 90 degrees.

In this test the tablet was laying flat on the table top with the top facing away from me.

I tilted the top down and raised the bottom up until the top was touching the table top and the bottom was straight up then returned it to the horizontal position.

That is the valley.

I then tilted the tablet toward me keeping the bottom touching the tabletop until the top was pointing up then and returned it to it's horizontal position.

That is the hill.

Roll - -90 to 90 degrees

Tablet was laying flat on the tabletop.

Tilted the screen to the right keeping the right side touching the table top then returned tablet face-up (valley)

Tilted the screen to the left keeping the left edge touching the table top then returned tablet face-up (hill).

At rest the reading should be zero.

Angle  ranges from -180 to 180 degrees.

The tablet was held with both hands -- top up with the screen facing me as if it were a steering wheel.

I then tilted turned or tilted the tablet to the left which caused the degrees to increase from 0 to 180.

I continued to rotate the tablet in a counterclockwise direction at which point 180 changed to -180 which is shown by the vertical line in the graph.

Continuing to turn in a counterclockwise direction, the values - now negative decreased from -180 to 0.

I stopped turning when the tablet was back to it's starting position.

Observations:

I can see how the Angle value would be useful for steering something in a game.

The jump between -180 and 180 could be avoided or filtered out if the 'steering wheel were limited to turning -90 to 90 degrees stop-to-stop for example.

I have already used the Azimuth value to make a simple digital magnetic compass.

It would be interesting to add the ability to correct for true north.

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> YouTube Video < 

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