CODEWITHSUNDEEP
androidandroid-sensors
tyczj
tyczj

Reputation: 73721

Get wearable device rotation in degrees from 0-360 around X axis

I am using the Rotation Vector sensor to try to track how many degrees rotation 0-360 around the X axis (aka wrist movement) the user moves.

I am using the SensorManagers getOrientation to the the yaw, pitch and roll this way

float[] rotationMatrix = new float[9];
SensorManager.getRotationMatrixFromVector(rotationMatrix, sensorData.getValues());

float[] orientation = new float[3];
SensorManager.getOrientation(rotationMatrix, orientation);

with the watch face pointing up it gives 0 degrees like I want but when I rotate I only get +/- 90 degree increments. rotating left gives me +90 degrees and rotating right gives me -90 degrees. I i continue rotating lets say from the +90 degrees I start getting negative degrees so when the watch is face down (180 degrees) is shows 0 again. using 90 degree increments is going to make it difficult to accurately get the actual rotation angle.

Is there a way to go from +/- 90 degree increments to 0-360 degrees?

Upvotes: 2

Views: 794

Answers (1)

DinoOcch
DinoOcch

Reputation: 430

You can use the z rotation value to find out whether the watch is face up or down. This determines the perspective you are viewing from and gives you 4 quadrants, instead of the 2 that you started with.

If z is positive: watch is face up. If z is negative, it is face down.

From here, you can create a coordinate system for conversion.

If the watch is facing up, coordinate is 90+x_rotation. Since rotating right gives [-90,0), and rotating left yields [0,90], this gives degrees of [-90+90,90+90] = [0, 180] Which is what we would expect of a watch facing up on the wrist.

If the watch is facing down, coordinate is 270+x_rotation. Quadrant 3 gives negative values of 90, making the values range from [270+-90,270] = [180,270]. Likewise, Quadrant 4 has positive values of 90, creating a range of [270,90+270]. So a watch facing down gives [180, 360].

Combined, we get the complete [0,360] device rotation range.

Hope this helps!

Upvotes: 1

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