Convert raw data to tilt angle value

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robypez
Posts: 5
Joined: 18:53, 01 Jul 2015

Convert raw data to tilt angle value

Postby robypez » 21:02, 04 Jul 2015

Hello, I'm creating my app.
I obtain with your api from the sensortag some value +/- 2.5, but I need to convert these value to degree. I want to check the tilt angle...

Any idea?

Image

ardiri
Posts: 58
Joined: 16:13, 28 May 2014

Re: Convert raw data to tilt angle value

Postby ardiri » 02:14, 09 Jul 2015

the tilt raw value should be between -1.0 and +1.0

you would need to understand what the raw data values actually mean; there is a good discussion of this on another forum:

http://www.i2cdevlib.com/forums/topic/4 ... gyrometer/

you will need to figure out if the relationship between 0 and +1 and -1 and 0 are linear in nature and map them to an angle between 0 and 90. maybe you can start a logging of raw values.. with different degree increments.. either find a pattern; or use a lookup table to convert the raw data into angles. there was a similar discussion on stack overflow which may shed some better light into how to map between raw and angles.

http://stackoverflow.com/questions/2371 ... elerometer

Code: Select all

float calcInclinationAngle(int iDataPos)
{
  float xVal = fAccel[0][iDataPos];
  float yVal = fAccel[1][iDataPos];
  float zVal = fAccel[2][iDataPos];
  float pitch = 0;
  //Pitch in radians
  pitch = atan2(xVal, sqrt(pow(yVal,2)+pow(zVal,2)));
  //Pitch in degrees
  pitch = pitch * 180/PI;
  return pitch;
}


you need to make sure the raw values are between -1.0 and +1.0 - if you are receiving other values you'll need to map them to this range.
// Aaron
Chief Technology Officer
Evothings AB http://www.evothings.com/


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