Protractor and angle gauge allows you to
measure any angle or slope. You can measure the angle between any
line and a vertical using a built-in gyroscope. Or you can measure
an angle based on the photo you made and nodes you selected. You
can learn exactly how sloped that Leaning Tower of Pisa actually
is. It is possible to recalibrate your device and use some line as
a base level for your measurements.