I have been doing a bit of research, but I cannot seem to find a way to determine small distances (centimeters and meters) using the sensors in Android or iOS devices. Bluetooth appears too inaccurate and require more than one device, GPS only works over larger variations in distance, and small variations in rotation seem to make using the accelerometer nearly impossible.

Is there a method that I am unaware of that would allow me to do such a thing? I am familiar with Calculus, so using Integrals to determine distance based on changes in time and velocity/ acceleration is not a problem for me, I just do not know how to determine those things.

Thank you.