Calibration does not always mean fixing a device, it sometimes means adjusting to solve a problem. In the early years of America, the famous Kentucky longrifles that conquered the frontier (and some British) had fixed sights. Since they couldn't be adjusted, frontiersmen - Kentucky was part of "The West" then - would adjust for wind, elevation and range by experience. If their shot was hitting low and left, they aimed high and right. Inference helped them get a better result.