Retired midlevel backline
Shoal TO; KR
The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is - whichever is greater - it obtains a difference or deviation. The guidance subsystem uses deviation to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position that it wasn't, it now is. Consequently, the missile must also know where it was. The missile guidance computance scenario works as follows: Because a variation has modified some of the information the missile has obtained, it is not sure just where it is, however it is sure where it isn't, within reason, and it knows where it was. It now subtracts where it should be from where it wasn't, or vice versa. And by determining the atmospheric conditions - the missile knows where it is.
