Clinometer

thingiverse

Measure Angles Based on Your Point of View. To accomplish this, print out a small protractor - one with sights that need to be aligned - and stick it to your object's side. Use It Like This: 1. Take a look at something interesting. 2. Line up the sighting mechanisms on your gadget with what you're looking at. 3. Now glance over to the side, where your 100mm (or about four inches) protractor has been pasted. That's how it works!