Clinometer is a free app that measures the vertical angle between your device and the ground, or a wall, building, tree, etc.

When you launch the app, you can choose to use the angle meter or select the angle through the settings screen. You can also use your phone's camera to measure angles, which will be displayed in the app.

You can measure the angle.

You can set the precision to 3 decimal places.

It is very easy to use.