This function can assist you to hang wall pictures or other paintings upright.

Click Cross Vertical Measure button to use this function. And you'll find a hint "Turn on the camera?".

If you choose NO, two mutually perpendicular reference lines help you to adjust paintings or others to upright. One line is always perpendicular to the ground and another one is always parallel to the ground no matter how your phone slopes.

If you choose YES, the phone's camera turns on and the picture camera catched will be displayed into the phone screen. It can help you to adjust angles intuitively.