android加速度传感器去除重力影响

这是android developer网站提供的方法 public void onSensorChanged(SensorEvent event) { // alpha is calculated as t / (t + dT) // with t， the low-pass filter's time-constant // and dT， the event delivery... 这是android developer网站提供的方法 public void onSensorChanged(SensorEvent event) { // alpha is calculated as t / (t + dT) // with t， the low-pass filter's time-constant // and dT， the event delivery rate final float alpha = 0.8; gravity[0] = alpha * gravity[0] + (1 - alpha) * event.values[0]; gravity[1] = alpha * gravity[1] + (1 - alpha) * event.values[1]; gravity[2] = alpha * gravity[2] + (1 - alpha) * event.values[2]; linear_acceleration[0] = event.values[0] - gravity[0]; linear_acceleration[1] = event.values[1] - gravity[1]; linear_acceleration[2] = event.values[2] - gravity[2]; } 请高手解释下，还有这个gravity初始值是多少，不能理解啊，不应该根据角度关系将重力分解到各个轴，再计算吗？