The missile knows where it is at all times. It knows this 8ecause it knows where it isn't. 8y su8tracting where it is from where it isn't, or where it isn't from where it is (whichever is gre8r), it o8tains a difference, or deviation. The guidance su8system uses deviations to gener8 corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't. In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation 8eing the difference 8etween where the missile is, and where it wasn't. If variation is considered to 8e a significant factor, it too may 8e corrected 8y the GEA. However, the missile must also know where it was. The missile guidance computer scenario works as follows. 8ecause a variation has modified some of the information the missile has o8tained, 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 su8tracts where it should 8e from where it wasn't, or vice-versa, and 8y differentiating this from the alge8raic sum of where it shouldn't 8e, and where it was, it is a8le to o8tain the deviation and its variation, which is called error.
::::)
Caption this Meme
