Minimum threshold for car accident

Question

I am using accelerometer to detect the car accident. I am having a problem with minimum threshold value is required to detect the car accident. What minimum threshold required to detect car accident.

@Override
public void onSensorChanged(SensorEvent event) {
    float x = event.values[0];
    float y = event.values[1];
    float z = event.values[2];

    float gX = x / 9.8f;
    float gY = y / 9.8f;
    float gZ = z / 9.8f;

    float gForce = FloatMath.sqrt(gX * gX + gY * gY + gZ * gZ);
    if(gForce > //HERE IS NEED THRESHOLD VALUE)
}

Answer 1

Acceleration required to deploy airbags

Around 20 - 30 G's. Of course it depends on your definition of "accident".

Source:

http://answers.google.com/answers/threadview/id/523539.html

Answer 2

Based on Googling around, I'd estimate a peak acceleration magnitude of >40G would indicate a car crash. See this this paper for a basic study of data during car crashes.

Alternatively, you could crash a few cars yourself and get some test data. :)