Ruler App: Camera Tape Measure is based on one of the most advanced technologies for smartphones at the moment. It is AR technology that will turn your camera into a ruler. You just need to point the camera at the objects you need to measure, choose a fixed point, and then move the camera. In general, this technology does not give you a truly 100% accurate number for practical or academic use. But it is 90% accurate to help you estimate the actual length of an object.