Its direction is the opposite direction of movement.

其方向与运动方向相反。

Then, using the difference  in angles and the time between measurements, the mouse determines the speed, angular distance  travelled, and direction of movement, and sends it to the computer.

然后， 利用角度差异和测量之间的时间，鼠标确定速度、行进的角距离和移动方向，并将其发送到计算机。