Precise Level is professional spirit level or just bubble level with nice bubble physics. After correct calibration you can go ahead and use this app tool instead a real spirit level. This bubble level is also a great tilt meter, angle meter professionally known as inclinometer. Any spirit level or inclinometer need calibration due to the production defects of mobile devices or just because of protruding camera. You can upgrade your spirit level to PRO version on whole day by watching short add or forever by purchase. After upgrade to PRO you have access to calibration guide and to the clipboard that store spirit level results.