 Calibration. Any procedure used to evaluate the accuracy of a measurement system? There's a certain amount of humor and recursiveness in a calibration procedure because you have to assume that your calibration procedure is correctly calibrating what it is you're trying to measure or the measurement tool that you're using. So really it's just about double checking that the measurement tool that you're using is actually working and it's measuring what it's supposed to measure and how it's supposed to measure. Just imagine a broken tape measure. It probably needs to be calibrated, right? Or a level that has a bubble stuck on one end. So no matter if it's up like this or up like this, the bubble's always on that side. So that would be that needs to be calibrated. A traditional compass doesn't need to be calibrated, but with these things called smartphones ironically you need to calibrate the compass. So just to make sure that it works because it's not really a compass. It's a representation of a compass and you need to make sure that anyway you get the idea. So how do we measure something? We need to calibrate it make sure that measure is accurate and then if it isn't accurate use that information to fix it.