hewwo!! ehehe the missiwe knows whewe iwt iws at aww times. Iwt knows thiws because iwt knows whewe iwt isn't. By subtwacting whewe iwt iws fwom whewe iwt isn't, ow whewe iwt isn't fwom whewe iwt iws (whichevew iws gweatew), iwt obtains a diffewence, ow deviation. The guidance subsystem uses deviations tuwu genewate cowwective commands tuwu dwive the missiwe fwom a position whewe iwt iws tuwu a position whewe iwt isn't, awnd awwiving at a position whewe iwt wasn't, iwt now iws. Consequentwy, the position whewe iwt iws, iws now the position thawt iwt wasn't, awnd iwt fowwows thawt the position thawt iwt was, iws now the position thawt iwt isn't. In the event thawt the position thawt iwt iws in iws nowt the position thawt iwt wasn't, the system has acquiwed a vawiation, the vawiation being the diffewence between whewe the missiwe iws, awnd whewe iwt wasn't. If vawiation iws considewed tuwu be a significant factow, iwt too may be cowwected by the gea. Howevew, the missiwe must awso know whewe iwt was.

the missiwe guidance computew scenawio wowks as fowwows. Because a vawiation has modified sowme of the infowmation the missiwe has obtained, iwt iws nowt suwe juwst whewe iwt iws. Howevew, iwt iws suwe whewe iwt isn't, within weason, awnd iwt knows whewe iwt was. Iwt now subtwacts whewe iwt shouwd be fwom whewe iwt wasn't, ow vice-vewsa, awnd by diffewentiating thiws fwom the awgebwaic sum of whewe iwt shouwdn't be, awnd whewe iwt was, iwt iws abwe tuwu obtain the deviation awnd its vawiation, which iws cawwed ewwow.